Semiconductor memory device with improved flexible redundancy scheme

ABSTRACT

A spare memory array having spare memory cells common to a plurality of normal sub-arrays having a plurality of normal memory cells is provided. A spare line in the spare array can replace a defective line in the plurality of normal sub-array. The defective line is efficiently repaired by replacement in an array divided into blocks or sub-arrays.

This application is a divisional of application Ser. No. 09/798,944,filed Mar. 6, 2001, now U.S. Pat. No. 6,449,199, which is a divisionalof Ser. No. 09/251,352, filed Feb. 17, 1999 now U.S. Pat. No. 6,233,181.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor memory devices,and more particularly, to a semiconductor memory device having a memoryarray divided into a plurality of memory blocks. More specifically, thepresent invention relates to a redundancy circuit for repairing adefective memory cell in a semiconductor memory device having such anarray-divided arrangement and a power supply circuit providedcorresponding to each block.

2. Description of the Background Art

In the semiconductor memory device, a defective memory cell is replacedwith a spare memory cell in order to equivalently repair the defectivememory cell to raise the yield of the products. A flexible redundancyscheme has been proposed in order to improve the use efficiencies ofspare lines (word lines or bit lines) and spare decoders for selectingspare lines in a redundancy circuit configuration including spare memorycells (spare word lines and bit lines) for repairing such defectivememory cells (see, for example, “A Flexible Redundancy Technique forHigh-Density DRAM's”, Horiguchi et al., IEEE Journal of Solid-StateCircuits, Vol. 26, No. 1, January 1991, pp. 12 to 17).

FIG. 53 is a schematic diagram of the general configuration of asemiconductor memory device having a conventional flexible redundancyscheme. In FIG. 53, the semiconductor memory device includes four memoryarrays MA0 to MA3. In each of memory arrays MA0 to MA3, a spare wordline to repair a defective memory cell row is provided. In memory arrayMA0, spare word lines SW00 and SW01 are provided, and in memory arrayMA1, spare word lines SW10 and SW11 are provided. In memory array MA2,spare word line SW20 and SW21 are provided, and in memory array MA3,spare word lines SW30 and SW31 are provided.

Row decoders X0 to X3 each for decoding an address signal to drive anormal word line provided corresponding to an addressed row into aselected state are provided corresponding to memory arrays MA0 to MA3. Acolumn decoder Y0 is provided between memory arrays MA0 and MA1 todecode a column address signal to select an addressed column, and also acolumn decoder Y1 is provided between memory arrays MA2 and MA3.

The semiconductor memory device further includes spare decoders SD0 toSD3 to store a row address at which a defective memory cell is present,maintain a word line (defective normal word line) corresponding to thisdefective row address in a non-selected state when the defective row isaddressed and drive a corresponding spare word line into a selectedstate, an OR circuit G0 to receive output signals from spare decodersSD0 and SD1, and an OR circuit G1 to receive output signals from sparedecoders SD2 and SD3.

The output signals of OR circuits G0 and G1 are provided in common tospare word line driving circuits included in row decoders X0 to X3.Spare decoders SD0 to SD3 are commonly provided with array addresssignal bits an-2 and an-1 to address one of memory arrays MA0 to MA3 andwith intra-array address signals bits a0 to an-3 to address a row in thememory array. Row decoders X0 to X3 are provided with array addresssignal bits an-2 and an-1, and a row decoder is activated when acorresponding memory array is addressed. OR circuits G0 and G1 eachcorrespond to two spare word lines provided for each of memory arraysMA0 to MA3.

Let us assume that normal word lines W0 and W1 are defective in memoryarray MA0, that a normal word line W2 in memory array MA1 is defective,and that a normal word line W3 in memory array MA2 is defective. In thisstate, the address of word line W0 is programmed in spare decoder SD0,while the address of word line W1 is programmed in spare decoder SD2.The address of normal word line W2 is programmed in spare decoder SD3,and the address of normal word line W3 is programmed in spare decoderSD1.

OR circuit G0 selects one of spare word lines SW00, SW10, SW20 and SW30,and the output signal of OR circuit G1 selects one of spare word linesSW1, SW1 , SW21 and SW31.

When normal word line W0 is addressed, the output signal of sparedecoder SD0 is driven into a selected state, and the output of ORcircuit G0 is activated. In this state, array address signal bits an-2and an-1 activate row decoder X0, and the remaining row decoders X1 toX3 are maintained in a non-active state. Thus, a word line drivingcircuit included in row decoder X0 drives spare word line SW00 into aselected state in response to the output signal of OR circuit G0. Atthis time, in row decoder X0, a decode circuit provided corresponding tonormal word line W0 is maintained in a non-active state. As a result,defective normal word line W0 is replaced with spare word line SW00.

If defective normal word line W1 is addressed, the output signal ofspare decoder SD2 attains an H level in a selected state, the outputsignal of OR circuit G1 attains an H level, and spare word line SW01 isselected If defective normal word line W2 is addressed, the outputsignal of spare decoder SD3 attains an H level in a selected state, theoutput signal of OR circuit G1 attains an H level, and spare word lineSW11 is selected. If defective normal word line W3 is addressed, theoutput signal of spare decoder SD1 attains an H level in a selectedstate, and spare word line SW20 is selected by OR circuit G0accordingly. More specifically, defective normal word lines W0, W1, W2and W3 are replaced with spare word lines SW00, SW01, SW11 and SW20,respectively.

In this flexible redundancy scheme shown in FIG. 53, a single spare wordline can be activated by any of a plurality of spare decoders. Forexample, spare word line SW20 can be driven into a selected state byspare decoder SD0 or SD1. A single spare decoder can drive any of aplurality of spare word line into a selected state. For example, sparedecoder SD0 can drive any of spare word lines SW00, SW10, SW20 and SW30into a selected state. Thus, the spare word line and spare decoders donot correspond in one-to-one relation, and therefore the spare wordlines and spare decoders can be more efficiently utilized. The number ofspare word lines and the number of spare row decoders in a single memoryarray may be selected independently from each other as long as thenumbers satisfy the following relation:

L≦R≦M·L/m

wherein M is the number of physical memory arrays, m the number ofmemory arrays whose defective normal word lines are replaced with spareword lines simultaneously, R the number of spare row decoders, and L thenumber of spare word lines in a single memory array. More specifically,M/m is the number of memory arrays which are logically independent fromone another. As a result, ML·L/m represents the number of spare wordlines which are logically independent from one another for the entirememory. Herein, the logically independent spare word lines are spareword lines selected by different row addresses. For example, in FIG. 53,if a normal word line is simultaneously selected in memory arrays MA0and MA2, memory arrays MA0 and MA2 are not logically independent fromeach other. In the arrangement shown in FIG. 53, L=2, R=4, M=4 and m=1.

By providing a spare row decoder common to memory arrays, a sparedecoder does not have to be provided for each of spare word lines, whichcan restrain the chip area from increasing.

The flexible redundancy scheme shown in FIG. 53 may be employed forrepairing a defective column as well. In repairing a defective column,the previously mentioned prior art document describes a method ofrepairing a defective column where a memory array is divided into aplurality of sub-arrays. The document particularly describes the way ofrepairing a defective column in multi-divided bit lines in ashared-sense amplifier arrangement and in a shared I/O scheme.

FIG. 54 is a schematic diagram of the configuration of an array portionin a semiconductor memory device according to a conventional flexibleredundancy scheme. In FIG. 54, two memory blocks MBi and MBi+1 areshown. Memory blocks MBi and MBi+1 each include a normal bit line pairBL and /BL provided corresponding to each memory cell column and a sparebit line (spare column) for repairing a defective column. In FIG. 54,the spare bit line included in the spare column is not clearly shown.

Normal bit lines BL and /BL at the same column address in memory blocksMBi and MBi+1 share a sense amplifier SA. A bit line isolation gate ILGis provided between sense amplifier SA and memory blocks MBi and MBi+1.Sense amplifier SA is connected to an internal data line pair I/Othrough an IO gate IOG which conducts in response to a column selectingsignal YS from column decoder Y. A memory block including a selectedmemory cell (MBi, for example) is connected to sense amplifier SA anddata is read out therefrom. In this case, a non-selected memory block(MBi+1) is disconnected from sense amplifier SA.

In the above-described shared-sense amplifier arrangement, a defectivecolumn address must be programmed for each of defects in normal bitlines, in a single memory block column selecting lines (YS lines) andsense amplifiers SA. For a normal bit line defect, the defective columnaddress is programmed on a memory block basis. For a sense amplifierdefect, the defective column address is so programmed as to use a sparecolumn for each of memory blocks MBi and MBi+1 which share thisdefective sense amplifier. For a column selecting line (YS line) defect,the defective column address is programmed for each of the memory blocksconnected to this column selecting line (YS line).

At the time of programming, in order to use a single spare columndecoder for a normal bit line defect, a sense amplifier defect and acolumn selecting line (YS line) defect, “Don't care” is programmed atthe time of programming a defective column address, an address tospecify a memory block is invalidated, and spare columns are replacedsimultaneously in a plurality of memory blocks.

In the previously mentioned document, a defective row is repaired byreplacing the defective row with a spare word line provided within amemory array including that defective row. Thus, a spare word line mustbe provided for each of memory arrays, and the spare word lines are notefficiently utilized. If a defective normal word line in one memoryarray is replaced with a spare word line in another memory array, thecontrol of the memory array related circuits will be complicated, andtherefore such arrangement must be avoided and is not considered at all.

In repairing a defective column, a spare column is provided for each ofmemory blocks, and spare columns are similarly not efficiently used.Although the shared I/O scheme has been considered for internal dataline arrangement, the way to repair a defective column in a memory arrayhaving a local/global hierarchical data line arrangement used in arecent block-divided arrangement has never been considered.

Meanwhile, in a conventional CMOS (Complimentary MOS) type semiconductordevice, the size of components (MOS transistor:insulated gate type fieldeffect transistor) is reduced to increase the integration density. Inorder to secure the reliability of the components thus miniaturized andto reduce the current consumed by the entire device, the power supplyvoltage is reduced. In order to allow the components to operate at ahigh speed, the threshold voltage of the MOS transistor must be lowereddepending upon the power supply voltage. This is because if the ratio ofthe threshold voltage to the power supply voltage is large, thetransition timing of the MOS transistor to the on state is delayed. If,however, the absolute value of the threshold voltage is lowered,sub-threshold leakage current to flow through the source-drain regionwhen the MOS transistor is turned off increases. This is for thefollowing reason. The threshold voltage is defined as the gate-sourcevoltage to allow a prescribed drain current to flow. In an n-channel MOStransistor, if the threshold voltage is lowered, the drain current-gatevoltage characteristic curve shifts toward the negative direction. Thesub-threshold current is represented by the current value when gatevoltage Vgs in the characteristic curve is 0V, and therefore thesub-threshold current increases as the threshold voltage is lowered.

When the semiconductor device operates, the ambient temperatureincreases, and the absolute value of the threshold voltage of the MOStransistor is lowered, resulting in more serious sub-threshold currentleakage. When this sub-threshold leakage current increases, the DCcurrent of the entire large scale integrated circuit increases, andparticularly in a dynamic type semiconductor memory device, the stand-bycurrent (current consumed in a stand-by state) increases.

In order to reduce the sub-threshold leakage current, amulti-threshold-voltage CMOS arrangement is employed.

FIG. 55 is a diagram showing a conventional multi-threshold-voltage CMOSarrangement by way of illustration. In FIG. 55, there are provided amain power supply line 902 transmitting a power supply voltage Vcc, asub-power supply line 904 coupled to main power supply line 902 througha p-channel MOS transistor 903, a main ground line 906 transmitting aground voltage Vss, and a sub-ground line 908 coupled to main groundline 906 through an n-channel MOS transistor 907. MOS transistor 903conducts when an activation signal /φACT is at an L level, while MOStransistor 907 conducts when an activation signal φACT is at an H level.MOS transistors 903 and 907 each have a relatively high thresholdvoltage (high-Vth). The internal circuit operates, with a voltage fromone of power supply lines 902 and 904 and a voltage from one of groundlines 906 and 908 used as both operation power supply voltages. In FIG.55, as the internal circuit, three-stage, cascaded inverter circuits 914a, 914 b and 914 c are shown. Inverter circuit 914 a includes ap-channel MOS transistor PQ having a source coupled to main power supplyline 902, and an n-channel MOS transistor NQ having a source coupled toground line 908. An input signal IN is provided in common to the gatesof MOS transistors PQ and NQ. Input signal IN is set to an L level in astand-by cycle.

Inverter circuit 914 b operates using voltages on sub-power supply line904 and main ground line 906 as both operation power supply voltages.Inverter circuit 914 c operates with voltages on main power supply line902 and sub-ground line 908 as both operation power supply voltages. MOStransistors PQ and NQ in each of these inverter circuits 914 a to 914 chave the absolute values of the threshold voltages set sufficientlysmall low-Vth). The operation of the circuit shown in FIG. 55 will benow described with reference to FIG. 56.

In a stand-by cycle, input signal IN is set to an L level. Controlsignal φACT is at an L level, and control signal /φACT is at an H level(Vcc level). In inverter circuit 914 b, MOS transistor PQ turns on, thesource and drain thereof are at the same voltage level, and therefore nocurrent is allowed to flow. Meanwhile, MOS transistor NQ is providedwith input signal IN at the ground voltage level at its gate and is inan off state. However, the sub threshold leakage current allowed to flowthrough MOS transistor 907 in an off state is sufficiently reduced,because the threshold voltage of the transistor 907 is high. As aresult, the sub-threshold current is reduced even if the thresholdvoltage of MOS transistor NQ is small. The sub-threshold current allowedto flow through MOS transistor 907 causes the voltage level onsub-ground line 908 to be higher than the ground voltage level, so thatthe gate-source region of MOS transistor NQ in inverter circuit 914 a isset to a reverse bias state, and its sub-threshold current is furtherreduced.

In inverter circuit 914 b, the input signal is at an H level, and MOStransistor NQ is turned on, the source and drain thereof are at the samevoltage level and therefore no sub threshold leakage current isgenerated. Meanwhile, p-channel MOS transistor PQ is provided with asignal at power supply voltage Vcc level at its gate to allowsub-threshold leakage current to flow. However, since MOS transistor 903is in an off state and MOS transistor 903 is a high-Vth transistor, thesub-threshold leakage current is sufficiently restrained. Thus, thesub-threshold leakage current in inverter circuit 914 b is restrained.The sub-threshold leakage current of MOS transistor 903 causes thevoltage level of sub-power supply line 904 to be lower than power supplyvoltage Vcc, and the gate-source region of MOS transistor PQ isreversedly biased in inverter circuit 914 b, the sub-threshold leakagecurrent of which is further restrained. Similarly to inverter circuit914 a, the sub-threshold leakage current is restrained in invertercircuit 914 c.

When an active cycle is started, control signal φACT attains an H level,control signal /φACT attains an L level, MOS transistors 903 and 907 areturned on, sub-power supply line 904 is coupled to main power supplyline 902, and sub-ground line 908 is coupled to main ground line 906.Thus, these inverter circuits 914 a to 914 c are supplied with a currentfrom a corresponding power supply line/ground line, their low-Vthtransistors operate at a high speed, and their output signals arechanged according to change in input signal IN.

In the power supply circuit arrangement as shown in FIG. 55, since thelogical level of an input signal in a stand-by cycle is previouslyknown, a connection path to a power source line is determinedaccordingly. If the logical state of input signal IN in a stand-by cycleis not predetermined, the logic gate is coupled to sub-power supply line904 and sub-ground line 908.

As disclosed in Japanese Patent Laying-Open No. 6-232348, in a DRAM(Dynamic Random Access Memory), circuits having the same circuitconfiguration such as decode circuits and word line drive circuits areprovided. As the storage capacity increases, the number of such circuitssignificantly increases. In repeating circuitry having repeatedlyprovided decode circuits and word line drive circuits, a prescribednumber of particular circuits (addressed circuits) are selectivelydriven among the circuits having the same configuration in response toan address signal. If these circuits are formed by low-Vth transistors,the power supply circuit arrangement as shown in FIG. 55 (hierarchicalpower supply arrangement: sub-threshold leakage current reducingcircuit) may be employed. In this case, as shown in FIG. 53,activation/inactivation of a power supply to a decoder or a word linedriver must be controlled for each of the blocks (because a word line isselected on a block basis.) Control signals φACT and /φACT are activatedwhen an active cycle is started. As a result, the number of circuitsconnected to sub-power supply line 904 or sub-ground line 908 increases,and as the parasitic capacitance increases, it takes longer time untilsub-power supply line 904 and sub-ground line 908 are driven toprescribed voltage (Vcc and ground voltage Vss) levels and therefore theoperation starting timings of the internal circuits should be delayeduntil these voltages becomes stable, which impedes high-speed accessingoperations.

As previously described, when a defective row/column is repaired using aspare decoder, a row/column to be selected is determined afterdetermining if a spare is to be used/not used. In this case, as shown inFIG. 53, if redundancy replacement is performed within the same block, acorresponding power supply circuit (a circuit transmitting any of thepower supply voltage and ground voltage) can be selected in response toan address signal to control the connection. If, however, a sparerow/column is used for repairing a defective cell in another memoryblock in the flexible redundancy arrangement, a memory block including amemory cell to be driven into a selected state must be specifiedaccording to a spare determination result, the power source voltage(power supply voltage and ground voltage) cannot be driven into a stablestate at a high speed, and high speed accessing operations cannot beimplemented.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an array-dividedsemiconductor memory device including a redundancy circuit, whichpermits the use efficiency of spare lines (spare word lines and sparebit line pairs) to be significantly improved.

Another object of the invention is to provide an array-dividedsemiconductor memory device including a redundancy circuit, whichpermits a defective normal line to be accurately repaired withouterroneous operation.

Yet another object of the present invention is to provide anarray-divided semiconductor memory device including a power supplycircuit without increasing accessing time and current consumption.

A further object of the present invention is to provide an array-dividedsemiconductor memory device including a redundancy circuit which permitsthe spare line use efficiency to be improved and a power supply circuitwhich permits accessing time and power consumption to be reduced.

Briefly stated, in a semiconductor memory device according to thepresent invention, spare lines are provided together as a single array,a plurality of memory mats are provided corresponding to the sparearrays, and a defective normal line in these plurality of memory mats ismade replaceable with a spare line in a corresponding spare array.

A power supply circuit corresponding to a spare block is driven into aselected state when an active cycle is started.

Furthermore, the selecting way of the power supply circuit is changedbetween a normal mode and a refresh mode.

By providing a spare array exclusively for a spare line, the spare linecan be shared among a plurality of memory blocks or sub arrays, andtherefore the use efficiency of the spare lines may be significantlyimproved over the case of providing a spare line for each memory blockor sub array.

In the array-divided arrangement, the selecting way of the power supplycircuit is changed between a normal mode and a refresh mode, the numbersof bits in an address signal to be decoded can be different, andtherefore the power supply circuit can be driven into a selected stateat a high speed in the normal mode. Meanwhile, since a high speedresponse is not required in the refresh mode, a large number of addresssignal bits are decoded to select a minimum necessary power supplycircuit and current consumption is reduced.

If a spare element is included, in the normal mode power supply switchcircuits for both a particular memory block including the spare elementand an addressed memory block are driven into a selected state, so thatthe power supply circuits can be driven into a selected state withouthaving to wait for a result of spare determination and that high speedaccessing operations are implemented.

In the refresh mode, the power supply circuit corresponding to a memoryblock including a memory cell to be selected is driven into a selectedstate according to the spare determination result, so that the number ofpower supply circuits to be selected in the refresh mode can be aminimum necessary number, and the current consumption can be reduced.Thus, a semiconductor memory device with improved use efficiency ofspare elements without increase accessing time and current consumptioncan be implemented.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a main part of a semiconductor memorydevice according to a first embodiment of the invention;

FIG. 2A is a schematic diagram depicting how a defective column in amemory array shown in FIG. 1 is repaired;

FIG. 2B is a schematic diagram of a spare decoder used for repairing adefective column;

FIG. 3A shows a modification of the spare decoder;

FIG. 3B is a diagram depicting how a defective column is repaired by thespare decoder shown in FIG. 3A;

FIG. 4 is a schematic diagram of an internal data reading portion in thearray arrangement shown in FIG. 1;

FIG. 5 is a schematic diagram of a main part of a semiconductor memorydevice according to a second embodiment of the invention;

FIG. 6 is a schematic diagram depicting how a normal local data bus anda normal global data bus are connected and a spare local data bus and aspare global data bus are connected in the memory array shown in FIG. 5;

FIG. 7 is a diagram showing the way to generate a spare local data busselecting signal;

FIG. 8 is a schematic diagram of a column selecting portion in a sparearray in the memory array shown in FIG. 5;

FIG. 9 is a schematic diagram of a main part of a semiconductor memorydevice according to a third embodiment of the invention;

FIG. 10 is a diagram showing how a defective row in the memory arrayshown in FIG. 9 is repaired by way of illustration;

FIG. 11 is a schematic diagram of an array portion in a semiconductormemory device according to a fourth embodiment of the invention;

FIG. 12 is a diagram showing the effect of a memory block arrangementshown in FIG. 11;

FIG. 13 is a schematic diagram of a bit line isolation instructionsignal generation portion for solving problems associated with thearrangement shown in FIG. 12;

FIG. 14 is a schematic diagram of a bit line isolation instructionsignal generation portion in the memory block arrangement shown in FIG.11;

FIG. 15 is a schematic diagram depicting how a defective normal row isreplaced with a spare row according to the fourth embodiment;

FIG. 16 is a diagram of a memory cell structure;

FIG. 17 is a schematic diagram of an array portion in a semiconductormemory device according to a fifth embodiment of the invention;

FIG. 18A shows the correspondence between address signal bits and aselected memory portion in a normal operation mode in the arrayarrangement shown in FIG. 17;

FIG. 18B shows the correspondence between address signal bits and aselected memory block in a test mode;

FIG. 19 is a schematic diagram of an example of a control portion toselect a memory block in the test mode shown in FIG. 18B;

FIG. 20 is a schematic diagram of a modification of the fifthembodiment;

FIG. 21A is a schematic diagram of a hierarchical power supplyarrangement 1 according to a sixth embodiment of the invention;

FIG. 21B is a diagram of a power switch circuit in a row-relatedperipheral circuit shown in FIG. 21A;

FIG. 22 is a schematic diagram of a memory array and a power switchcircuit according to the sixth embodiment;

FIG. 23A is a diagram showing the selected state of a power switchcircuit in a normal mode in hierarchical power supply arrangement 1according to the sixth embodiment;

FIG. 23B is a waveform diagram representing the operation;

FIG. 24 is a schematic diagram of the selected state of the hierarchicalpower supply arrangement in FIG. 22 in a refresh mode;

FIG. 25 is a schematic diagram of a row-related control portion in thesemiconductor memory device according to the sixth embodiment;

FIG. 26 is a diagram of an example of a power supply block decoder shownin FIG. 21;

FIG. 27 is a diagram of a power supply block decode circuit for a powersupply block selecting signal φB2;

FIG. 28 is a schematic diagram depicting how address bits are allocatedin hierarchical power supply arrangement 1 according to the sixthembodiment;

FIG. 29 is a diagram of a modification of the hierarchical power supplyarrangement according to the sixth embodiment;

FIG. 30 is a signal waveform diagram representing the operation of thehierarchical power supply arrangement shown in FIG. 29;

FIG. 31 is a diagram of a repeating circuit in a row-related peripheralcircuit in the modification of hierarchical power supply arrangement 1;

FIGS. 32A and 32B are diagrams showing the selected states of the powerswitch circuit in a normal mode and a refresh mode, respectively in ahierarchical power supply arrangement 2 according to the sixthembodiment of the invention;

FIG. 33 is a schematic diagram of a power supply block decoder for FIGS.32A and 32B;

FIG. 34 is a diagram of a power block decode circuit for a particularpower supply block selecting signal φB2;

FIG. 35 is a schematic diagram of a modification of hierarchical powersupply arrangement 2 according to the sixth embodiment;

FIG. 36 is a schematic diagram of a control portion in a hierarchicalpower supply arrangement 3 according to the sixth embodiment;

FIG. 37 is a signal waveform chart representing the operation ofhierarchical power supply arrangement 3 according to the sixthembodiment;

FIG. 38 is a diagram of an example of a power supply block decoder shownin FIG. 36;

FIG. 39 is a diagram of an example of a register shown in FIG. 36;

FIG. 40 is a schematic diagram of an example of a count up instructionsignal generation portion shown in FIG. 36;

FIG. 41 is a schematic diagram of hierarchical power supply arrangement1 according to a seventh embodiment of the invention;

FIG. 42 is a schematic diagram showing the selected state of the powerswitch circuit in hierarchical power supply arrangement 1 according tothe seventh embodiment in a normal mode;

FIG. 43 is a signal waveform diagram representing the operation when thepower switch circuit shown in FIG. 42 is selected;

FIG. 44 is a schematic diagram showing the selected state of the powersupply switch circuit and hierarchical power supply arrangement 1according to the seventh embodiment in a refresh mode;

FIG. 45 is a signal waveform diagram representing the operationcorresponding to the selected state of the memory switch circuit shownin FIG. 44;

FIG. 46A is a diagram of an example of the power block decoder inhierarchical power supply arrangement 1 according to the seventhembodiment;

FIG. 46B is a signal waveform diagram representing the operation of thepower supply block decode circuit shown in FIG. 46A;

FIG. 47A is a diagram of a power supply block decoder in hierarchicalpower supply arrangement 1 according to the seventh embodiment;

FIG. 47B is a signal waveform diagram representing the operation of thepower supply block decoder shown in FIG. 47A;

FIG. 48 is a schematic diagram of a modification of hierarchical powersupply arrangement 1 according to the seventh embodiment;

FIG. 49 is a schematic diagram of a control portion in hierarchicalpower supply arrangement 2 according to the seventh embodiment;

FIGS. 50A and 50B are schematic diagrams showing the selected state ofpower supply switch circuits in hierarchical power supply arrangement 2according to the seventh embodiment;

FIG. 51A is a diagram of the power supply block decode circuit inhierarchical power supply arrangement 2 according to the seventhembodiment;

FIG. 51B is a waveform diagram representing the operation of the circuitof FIG. 51A;

FIG. 52 is a diagram of the power supply block decoder in hierarchicalpower supply arrangement 2 according to the seventh embodiment;

FIG. 53 is a schematic diagram of an array portion in a semiconductormemory device with a conventional flexible row redundancy arrangement;

FIG. 54 is a schematic diagram of an array portion in a conventionalflexible column redundancy arrangement;

FIG. 55 is a diagram of an example of a conventional hierarchical powersupply arrangement; and

FIG. 56 is a waveform diagram representing the operation of thehierarchical power supply arrangement shown in FIG. 55.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1 is a schematic diagram of an array portion in a semiconductormemory device according to a first embodiment of the invention. In FIG.1, a memory array is divided into a plurality of sense amplifier blocks(row blocks) RB#0 to RB#m. These row blocks RB#0 to RB#m each share wordlines. Row blocks RB#0 to RB#m are each divided into a plurality ofsub-arrays. Row block RB#i (i=0 to m) is divided into normal sub-arraysMB#i0 to MB#in. These normal sub-arrays MB#i0 to MB#in each have aplurality of memory cells arranged in a matrix of rows and columns andshare word lines (rows). A sensing operation is performed on the basisof a sense amplifier block.

Row blocks RB#0 to RB#m are provided with spare arrays SP#0 to SP#mrespectively to repair a defective column (a column including adefective normal memory cell) in corresponding row blocks RB#0 to RB#m.These spare arrays SP#0 to SP#m each have memory cells (spare memorycells) arranged in a plurality of columns. (The number of rows of sparearrays SB#0 to SB#m is the same as the number of rows of memory cellsincluded in a normal sub-array.)

Normal local data buses LIO00 to LIOmn are provided to normal sub-arraysMB#00 to MB#mn, respectively. These normal local data buses LIO00 toLIOmn communicate data only with corresponding normal sub-arrays MB#00to MB#mn.

Normal sub-arrays arranged in alignment along the column direction formcolumn blocks CB#0 to CB#n. Spare local data buses SIO0 to SIOm aresimilarly provided to spare arrays SP#0 to SP#m. These spare local databuses SIO0 to SIOm communicate data only with corresponding spare arraysSP#0 to SP#m. Normal global data buses NGIO0 to NGIOn are provided tonormal sub-arrays arranged in alignment in the column direction, inother words, to column blocks CB#0 to CB#n, respectively. These normalglobal data buses NGIO0 to NGIOn are coupled to normal local data busesprovided for normal sub-arrays in corresponding column blocks throughrespective block selecting gates BSG. Block selecting gate BSG conductsin response to a corresponding block selecting signal to connect acorresponding normal local data bus and a corresponding normal globaldata bus, when a corresponding row block is selected. Spare local databuses SIO0 to SIOm are also coupled to spare global data bus SGIOthrough corresponding block selecting gates BSG. Block selecting gatesBSG provided for spare arrays SP#0 to SP#m each conduct when acorresponding row block is selected, to connect a corresponding sparelocal data bus to spare global data bus SGIO.

By providing a spare array SP#i common to normal sub-arrays MB#i0 toMB#in in row block RB#i, spare columns included in spare array SP#i canbe used for normal sub-arrays MB#i0 to MB#in, so that the use efficiencyof spare columns is improved.

When a spare column is provided for each of normal sub-arrays and moredefective columns than the spare columns provided in a normal sub-arrayare present, the defective columns can not be repaired. However, if, asshown in FIG. 1, spare arrays are provided and spare columns arecollectively provided, a large number of defective columns present in anormal sub-array can be repaired by replacing the defective column witha spare column in a corresponding spare array, which improves the yieldsof the products.

FIG. 2A is a diagram showing how a defective normal column is repairedby way of illustration. In FIG. 2A, spare arrays SP#0 to SP#m eachinclude four spare bit line pairs (spare columns) SBL0 to SBL3.

Column decode circuits Y0 to Yn are provided for column blocks CB#0 toCB#n, respectively. A spare decode circuit SPD is provided for spareblock SP#. Column decode circuits Y0 to Yn transmit a column selectingsignal through a column selecting line CSL common to memory sub-arraysincluded in a corresponding column block. Spare decode circuit SPDtransmits a spare column selecting signal through spare column selectinglines SCSL0 to SCSL3 provided for spare bit line pairs SBL0 to SBL3,respectively. Let us now assume that normal columns (normal bit linepairs) are repaired by replacement independently from one another innormal memory sub-arrays MB#00 to MB#mn.

FIG. 2B is a diagram showing an example of spare decode circuit SPDshown in FIG. 2A. In FIG. 2B, spare decode circuit SPD includes ORcircuits OG0 to OG3 provided corresponding to spare column selectinglines SCSL0 to SCSL3, respectively. For each of OR circuits OG0 to OG3,spare decoders provided corresponding to row block RB#0 to RB#m aredisposed. For OR circuit OG0, spare decoders SG00 to SG0m are provided,and for OR circuit OG3, spare decoders SD30 to SD3m are provided. Adefective normal bit line pair in each row block is programmed in aspare decoder provided for each OR circuit.

Now, as shown in FIG. 2A, normal bit line pair PBL0 in memory sub-arrayMB#00 is replaced with spare bit line pair SBL0 in spare array SP#0, andnormal bit line pair PBL1 in memory sub-array MB#0n is replaced withspare bit line pair SBL1 in spare array SP#0. Normal bit line pair PBL2in memory sub-array MB#10 is replaced with spare bit line pair SBL0 inspare array SP#1, and defective normal bit line pairs PBL3 and PBL4included in memory sub-arrays MB#m0 and MB#mn respectively are replacedwith spare bit line pairs SBL0 and SBL3 in spare array SP#m. In thiscase, the address of defective normal bit line pair PBL0 is programmedin spare decoder SD00, and the address of defective normal bit line pairPBL1 is programmed in the spare decoder provided for an OR circuitprovided corresponding to spare column selecting lines CSL1. Defectivenormal bit line pair PBL2 has its address programmed in spare decoderSD01 provided for OR circuit OG0. Defective normal bit line pairs PBL3and PBL4 have their addresses programmed in spare decoders SD0m andSD3m. As a result, when a defective normal bit line pair is addressed, acorresponding spare column selecting line is driven into a selectedstate. At this time, according to the output signals of these ORcircuits, the decoding operations of column decode circuits Y0 to Yn arestopped. More specifically, the use of the spare decode circuit shown inFIG. 2B permits defective normal bit line pairs to be repairedindependently from one another among memory sub-arrays MB#00 to MB#mn.

In the configuration of the spare decode circuit shown in FIG. 2B, theaddress of a defective normal bit line pair can be programmed for eachrow block. It is therefore not requested that the spare decoders eachstore “Don't care” state. If normal column selecting line CSL isdefective, each spare decoder has only to be programmed with the sameaddress signal. In this case, however, by providing the spare decoderwith the function of storing the “Don't care” state, defective normalbit line pairs can be repaired on a row block basis and defective normalbit line pairs can be also repaired by replacing a defective normalcolumn selecting line as well.

Modification

FIG. 3A is a diagram of a modification of the spare decode circuit shownin FIG. 2A. In FIG. 3A, a spare decoder is disposed for a column block.More specifically, for OR circuit 0G0, spare decoders SD00 to SD0n areprovided, while for OR circuit OG3, spare decoders SD30 to SD3n areprovided. Spare decoders SD00 to SD0n correspond to column blocks CB#0to CB#n, respectively, while spare decoders SD30 to SD3n correspond tocolumn blocks CB#0 to CB#n, respectively.

Let us now assume that a normal bit line pair PBLO in memory sub-arrayMB#00 is defective, and that a column selecting line CSL from columndecode circuit Yn is defective. In this case, the address of defectivenormal bit line pair PBL0 is programmed in spare decoder SD00, and theaddress of defective normal column selecting line CSL is programmed inspare decoder SD3n. When the address of defective normal columnselecting line CSL is programmed, spare decoder SD3n has its columnblock address bit invalidated, and the output signal of spare decoderSD3n indicates a selected state if a normal bit line pair correspondingto a defective column selecting line CSL in any of memory sub-arraysMB#0n to MB#mn in column block CB#n is addressed.

In this case, defective normal bit line pair PBL0 is replaced with sparebit line pair SBL0 in spare array SP#0, and defective normal columnselecting line CSL from column decode circuit Yn is replaced with sparecolumn selecting line SCSL3.

Note that in the arrangement shown in FIG. 1, a single memory sub-arrayis selected and connected to a corresponding normal global data bus. Asa result, 1-bit data is input/output.

FIG. 4 is a schematic diagram of a data reading portion. In FIG. 4, mainamplifiers MAP0 to MAPn are provided to normal global data buses NGIO0to NGIOn, respectively, and a spare main amplifier MAPs is providedcorresponding to a spare global data bus SGIO. Main amplifier MAP0 toMAPn are selectively activated in response to activation of mainamplifier activation signals PAE0 to PAEn, and spare main amplifier MAPsis activated in response to a spare main amplifier activation signalPAEs. When spare main amplifier activation signal PAEs is activated,main amplifier activation signals PAE0 to PAEn are all maintained in anon-active state. Thus, when a defective bit is repaired by replacement,1-bit data can be accurately read out. In order to write data, a writedriver has only to be provided in place of a main amplifier.

Spare main amplifier activation signal PAEs is activated when any of theoutput signals of OR circuits OG0 to OG3 attains an H level.

Note that in the configuration of the reading portion in FIG. 4, normalglobal data buses NGIO0 to NGIOn are connected to normal local databuses provided corresponding to a selected row block. However, sinceonly one of column decode circuits Y0 to Yn transmits an activatedcolumn selecting signal onto a column selecting line, only one of normalglobal data buses NGIO0 to NGIOn receives the data of a selected memorycell (when a normal memory cell is accessed).

If all the memory sub-arrays are selected in a selected row block, aspare local data bus is provided for each of the spare sub-bit linepairs in each spare array, and spare global data buses are providedcorresponding to these plurality of spare local data buses. Using sparedecoders SD00 to SD3n having the configuration shown in FIG. 3A, one ofthe spare main amplifiers provided for the plurality of spare globaldata buses is selectively activated. Alternatively, using the outputsignals of these spare decoders SD00 to SD3n, a column block at which adefective normal column has been repaired is detected, and the outputsignal of the spare main amplifier provided for the detected columnblock is selected and transmitted. This can be implemented by using aswitch circuit.

In FIGS. 2A and 3A, spare decoders are used for row blocks or columnblocks. However, the number of spare decoders can be suitably determineddepending upon the number of defective normal bit line pairs to berepaired in the entire memory array.

The number of spare bit line pairs in each of spare arrays SP#0 to SP#mcan be suitably determined. What is required is that a plurality ofspare bit line pairs are provided per column block.

As described above, according to the first embodiment of the invention,a spare array is provided for each row block, and an arbitrary defectivenormal column in a plurality of sub-arrays included in a correspondingrow block can be repaired, so that defective normal columns can beefficiently repaired in each row block.

A spare decoder to select a spare column (spare bit line pair) is sharedamong a plurality of memory sub-arrays, in other words, a spare decoderis not necessary for each of memory sub-arrays, which reduces thecircuit occupying area and improves the use efficiency of sparedecoders.

Second Embodiment

FIG. 5 is a schematic diagram of a memory array portion in asemiconductor memory device according to a second embodiment of theinvention. In the array arrangement shown in FIG. 5, block selectinggates BSGs provided corresponding to spare arrays SP#0 to SP#m receivesignals φso to φsm different from signals φ0 to φm to select acorresponding row block. More specifically, when a defective normalcolumn is repaired, a prescribed number of spare local data buses amongspare local data buses SIO0 to SIOm are simultaneously connected tospare global data bus SGIO. The other arrangement is the same as that inFIG. 1, and corresponding portions are denoted by the same referencecharacters.

FIG. 6 is a schematic diagram depicting how normal global data buses areconnected to local data buses and spare local data buses. In FIG. 6,normal global data bus NGIO is connected to a local data bus LIOithrough a block selecting gate BSG. Block selecting gate BSG conducts inresponse to a row block selecting signal φi. Meanwhile, spare globaldata bus SGIO is connected to spare local data bus SIOi through spareblock selecting gate BSGs and at the same time connected to a pluralityof spare local data buses. FIG. 6 generically shows spare local data busSIOj connected to spare global data buses SGIO by way of illustration.

In a memory sub-array, normal memory cells are arranged in a matrix ofrows and columns. In a spare-array, spare memory cells are arranged in amatrix of rows and columns. The number of columns in the spare array,however, is significantly smaller than the number of columns in a normalsub-array, because the spare array is provided to repair a defectivecolumn in a normal sub-array in a corresponding row block. As a result,when parasitic capacitance Ca is connected to bus lines to local databus LIOi, smaller parasitic capacitance Cc is present at bus lines ofspare local data bus SIOi.

Meanwhile, normal global data bus NGIO and spare global data bus SGIOare provided extending in the column direction in a memory array, andalmost the same parasitic capacitance Cb is present on these buses. As aresult, if only a single spare local data bus is connected to spareglobal data bus SGIO, the parasitic capacitance produced is Cb+Cc. Atthe time of accessing a normal memory cell, the parasitic capacitanceproduced on the bus line is Ca+Cb. At the time of accessing a sparememory cell, the parasitic capacitance on the bus is small, a signalchanges in a timing faster than that in accessing a normal memory cell.Therefore, signal propagation delay is different between normal memorycell accessing and spare column selecting, the timings of changes in theinternal signals are different, which could cause inconsistency ininternal timings and erroneous operations. Particularly in the casewhere memory array as shown in FIG. 5 is provided in plurality andmultiple-bit data is input/output, if a spare column is selected in amemory array and a normal column is selected in another memory array,the timings of transferring data are different, and therefore the setup/hold time of internal data could be different, which destabilizes thecircuit operations.

Also when columns are selected sequentially in synchronization with aclock signal, data is externally read out alternately after it is readand latched in parallel with selected data in another memory cell array.If the transmission time of a data signal is different for selecting anormal memory cell and for selecting a spare column, the set up/holdtime relative to the latch timing is different, which could make itdifficult to read out data accurately.

Thus, as shown in FIG. 6, at the time of accessing a defective sparememory cell, a plurality of spare local data buses are simultaneouslyconnected to spare global data bus SGIO. Thus, the signal propagationdelay time is made equal between the case of selecting a normal memorycell and the case of accessing a spare memory cell.

The number of spare local data buses k driven simultaneously into aselected state is specifically given by the following expression:

Cb+Ca=Cb+k·Cc

Therefore the following expression results:

Ca=k·Cc

Thus, the problems associated with mismatch in the timings can beavoided.

Let us now assume that eight row blocks RB#0 to RB#7 are provided asshown in FIG. 7. Row blocks RB#0 to RB#7 are addressed by 3 addresssignal bits, ai, aj and ak. These 3 address signal bits, ai, aj and akare decoded to generate a block selecting signal φi.

One of the group of row blocks RB#0 to RB#3 and the group of row blocksRB#4 to RB#7 is addressed by address signal bit ai, one of the group ofrow blocks RB#0, RB#1, RB#4 and RB#5 and the group of row blocks RB#2,RB#3m RB#6 and RB#7 is addressed by address signal bit aj, and one ofthe group of row blocks RB#0, RB#2, RB#4 and RB#6 and the group of rowblocks RB#1, RB#3, RB#5 and RB#7 is addressed by address signal bit ak.In this case, address signal bits ai to ak can be suitably invalidated(set to a “Don't care” state) to generate spare array block selectingsignal φsi.

If, for example, address signal bit ak is invalidated, two row blocksare simultaneously addressed, two spare local data buses can beconnected to a spare global data bus. If address signal bit aj isinvalidated, two row blocks can be similarly addressed. If addresssignal bits aj and ak are both invalidated, four row blocks can besimultaneously addressed. If 3 address signal bits ai to ak are allinvalidated, all the row blocks can be addressed. Thus, by the use ofthis arrangement, spare local data buses for a necessary number(multiples of 2) of spare arrays can be connected to the spare globaldata bus.

FIG. 8 is a schematic diagram of a column selecting portion in a spareblock. In FIG. 8, the configuration of two spare arrays SP#i and SP#j isshown.

Referring to FIG. 8, in spare array SP#i, a spare column selecting gateCSGi conducts to connect a spare bit line pair SBL to spare local databus SIOi in response to a local column selecting signal YSi output froman AND circuit SCGi which in turn receives a column selecting signal anda row block address signal φi from a spare column decode circuit whichis not shown. In spare array SP#j, a spare column selecting gate CSGjconducts to connect a spare bit line pair SBL and spare local data busSIOj in response to a spare local column selecting signal YSj from anAND circuit SCGj which in turn receives a spare column selecting signaland a row block selecting signal φj transmitted onto a spare columnselecting line SCSL from the spare column decode circuit. Spare localdata buses SIOi to SIOj are connected to spare global data bus SGIOthrough spare block selecting gates BSGs which conduct in response toblock selecting signals φsi and φsj.

In the configuration shown in FIG. 8, when a spare array is accessed,spare local data buses SIOi to SIOj are coupled to spare global data busSGIO in parallel. In this state, a spare bit line pair SBL for a sparearray provided corresponding to a selected row block is connected to acorresponding spare local data bus. Thus, if a spare column selectingsignal applied onto spare column selecting line SCSL from the sparecolumn decode circuit is provided in common to spare arrays SP#0 t SP#mand a plurality of spare local data buses are simultaneously connectedto the spare global data bus, a spare column corresponding to anaddressed defective column can be accurately selected for dataaccessing. Thus, such a situation can be prevented that a spare bit linepair held in a precharge state is connected to the spare global data busthrough a corresponding spare local data bus and the spare memory datais destroyed.

In the foregoing description, an address signal bit for addressing a rowblock is set to a degenerated state (Don't care state) and a pluralityof spare local data buses are simultaneously connected to the-spareglobal data bus. However, a decode circuit may be separately provided,and a set of spare local data buses selected at a time for eachaddressing of a row block may be determined based on the output of thedecode circuit.

As described above, according to the second embodiment, a plurality ofspare local data buses are connected to the spare global data bus inparallel, the signal propagation delay for the global data bus can bethe same for accessing a normal memory cell and for accessing a sparememory cell, so that the problems associated with mismatch in theinternal timings can be avoided and a stably operating semiconductormemory device can be implemented.

Third Embodiment

FIG. 9 is a schematic diagram of a main part of a semiconductor memorydevice according to a third embodiment of the invention. In FIG. 9, amemory array is divided into a plurality of row blocks (sense amplifierblocks) RBX#0 to RBX#m along the column direction. Row blocks RBX#1 toRBX#m are formed by normal memory sub-arrays MA#1 to MA#m having normalmemory cells arranged in a matrix of rows and columns. Row block RBX0includes a normal memory sub-array MA#0 having normal memory cellsarranged in a matrix of rows and columns, and a spare array SPX# havingspare memory cells arranged in a plurality of rows and sharing thecolumns with normal memory sub-array MA#0. The plurality of spare rows(spare word lines) included in spare array SPX# can replace defectivenormal word lines included in normal memory sub-arrays MA#0 to MA#m. Rowdecoders X0 to Xm are provided for normal memory sub-arrays MA#0 toMA#m, respectively, and a spare row decode circuit SPDX is provided forspare array SPX#.

In the configuration shown in FIG. 9, spare array SPX# is provided incommon to normal memory sub-arrays MA#0 to MA#m. As a result, ifdefective rows concentrate in one normal memory sub-array, spare wordlines included in spare array SPX# can be used for repairing byreplacement, and therefore the yields of the products can be improved. Aspare row decoder is shared among a plurality of normal memorysub-arrays (row blocks) and therefore the number of spare decoders canbe reduced.

FIG. 10 is a schematic diagram of spare row decode circuit SPDX shown inFIG. 9. FIG. 10 shows the configuration of spare row decode circuit SPDXwhen four spare word lines SWL0 to SWL3 are provided by way ofillustration. Spare row decode circuit SPDX includes spare row decodersSDX0 to SDX3 provided corresponding to spare word lines SWL0 to SWL3,respectively. These spare row decoders SDX0 to SDX3 are programmed withboth a block address to address a memory sub-array and a row address toaddress a row in a sub-array.

Let us now assume that a defective normal word line WL0 included innormal memory sub-array MA#0, defective normal word lines WL1 and WL2included in normal memory sub-array MA#1, and a defective normal wordline WL3 included in normal memory sub-array MA#m are repaired byreplacement with spare word lines as shown in FIG. 10. In this case, theaddress (including a block address) of word line WL0 is programmed inspare row decoder SDX0, and the addresses of defective normal word linesWL1 and WL2 are programmed in spare row decoders SDX1 and SDX2,respectively, and the address of defective normal word line WL3 isprogrammed in spare row decoder SDX3. Therefore, defective normal wordlines WL0, WL1, WL2 and WL3 are replaced with spare word lines SWL0 ,SWL1, SWL2 and SWL3, respectively.

Thus, since a spare row decoder is shared among normal memory sub-arraysMA#0 to MA#m, a spare row decoder is not necessary for each of thenormal memory sub-arrays, and therefore increase in the array occupiedarea can be restrained. Since spare word lines are shared among normalmemory sub-arrays MA#0 to MA#m, and therefore the use efficiency ofspare word lines can be improved.

By providing spare array SPX# in common to normal memory sub-arrays MA#0to MA#m in row block RBX#0, spare word line SWL included in spare arraySPX# can be used by an arbitrary normal memory sub-array, and the useefficiency of spare word lines can be improved.

Since spare array SPX# is included in normal memory sub-array MA#0, asense amplifier provided for row block RBX0 has only to be activatedwhen one of spare decoders SDX0 to SDX3 is selected, and therefore thecontrol operation of the sense amplifier is simplified.

In the configuration shown in FIGS. 9 and 10, one row block is selectedamong row blocks RBX#0 to RBXm for sensing operation. (A word line isselected.)

The number of spare word lines SWL included in spare array SPX# isarbitrary.

As in the foregoing, according to the third embodiment of the invention,spare word lines are collectively provided in a single spare array forcommon use among a plurality of normal memory sub-arrays, the number ofspare row decoders is reduced, and the use efficiency of spare wordlines is improved.

Fourth Embodiment

FIG. 11 is a schematic diagram of an array portion in a semiconductormemory device according to a fourth embodiment of the invention. In FIG.11, a memory array includes normal memory sub-arrays MA#0-0 to MA#0-Nand normal memory sub-arrays MA#1-0 to MA#1-N provided in the columndirection, alternately with normal memory sub-arrays MA#0-0 to MA#0-N. Aspare array SPX#0 having a prescribed number of spare word lines SWL isprovided for normal memory sub-array MA#0-0 to form one row block (senseamplifier block) RBX0, while in normal memory sub-array MA#1-N, a sparearray SPX#1 having a prescribed number of spare word lines SWL isprovided to form a row block RBX#1. Normal memory sub-arrays MA#0-0 toMA#0-N and MA#1-0 to MA#1-N each have normal memory cells arranged in amatrix of rows and columns.

Sense amplifier bands SAB1 to SABm are provided between memorysub-arrays adjacent to one another in the column direction. A senseamplifier band SABO is provided outside normal memory sub-array MA#0-0,and a sense amplifier band SABm+1 is provided adjacent to normal memorysub-array MA#1-N.

These sense amplifier bands SAB0 to SABm+1 have an alternate sharedsense amplifier arrangement. When one normal memory sub-array or rowblock is selected, the sense amplifiers included in the sense amplifierbands provided on both sides are used for sensing operation.

Spare word lines in spare array SPX0 included in row block RBX#0 canreplace normal word lines included in memory sub-arrays MA#0-0 toMA#0-N, and each spare word line in spare array SPX#1 provided in normalmemory sub-array MA#1-N can replace each normal word line included innormal memory sub-arrays MA#1-0 to MA#1-N.

In a normal operation, one of normal memory sub-arrays MA#0-0 to MA#0-Nis selected or one of normal memory sub-arrays MA#1-0 to MA#1-N isselected. More specifically, in the arrangement shown in FIG. 11, onenormal memory sub-array is driven into a selected state. Now, advantagesbrought about by alternately arranging normal memory sub-arrays MA#0-0to MA#0-N and normal memory sub-arrays MA#1-0 to MA#1-N in the columndirection and providing a spare array for each of the groups ofsub-arrays will be described.

Let us now assume that spare word lines in spare array SPX# included inrow block RBX0 as shown in FIG. 12 can replace defective normal wordlines in all the normal memory sub-arrays. In the shared sense amplifierarrangement, row block RBX0 and normal memory sub-array MA#1-0 areprovided on both sides of sense amplifier band SAB1. A bit lineisolation gate BLIG0 is provided between sense amplifier band SAB1 androw block RBX0, and a bit line isolation gate BLIG1 is provided betweensense amplifier band SAB1 and normal memory sub-array MA#1-0. Bit lineisolation gate BLIG0 is supplied with the output signal of NOR circuitOGa receiving a replacement instruction signal/φsp and a sub-arraysub-array designating signal φ1 as a bit line isolation control signal.

Bit line isolation gate BLIG1 is supplied with the output signal of anNOR circuit OGb receiving replacement instruction signal φsp andsub-array designating signal φ0 as a bit line isolation instructionsignal. Replacement instruction signal φsp is selectively pulled to an Hlevel, active state when a defective normal cell is addressed and aspare word line included in spare array SPX# is selected. Sub-arraydesignating signal φ1 attains an active state, H level, when normalmemory sub-array MA#1-0 is addressed, and sub-array designating signalφ0 attains an active state, H level, when normal memory sub-array MA#0-0is addressed.

Let us assume that a defective normal word line included in normalmemory sub-array MA#1-0 is replaced with a spare word line included inspare array SPX#. When this defective normal word line in normal memorysub-array MA#1-0 is addressed, sub-array address signal φ1 attains an Hlevel, while sub-array designating signal φ0 maintains an L level. As aresult, the output signal of NOR circuit OGa attains an L level, bitline isolation gate BLIG0 attains a non-conductive state, the sparearray SPX# is disconnected from sense amplifier band SAB1. Meanwhile,the defective normal word line is replaced with a spare word lineincluded in spare array SPX#, replacement instruction signal φsp isdriven into an H level, therefore the output signal of NOR circuit OGbattains an H level, and bit line isolation gate BLIG1 attains anon-conductive state. As a result, sense amplifier band SAB1 isdisconnected from both spare array SPX# and normal memory sub-arrayMA#1-0, and the defective normal word line cannot be repaired.

For the purpose of avoiding this situation, the circuit shown in FIG. 13could be used as the bit line isolation control circuit in order to turnon bit line isolation gate BLIG0 when a spare word line is used.

In FIG. 13, the bit line isolation control circuit includes an inverterOGaa which receives sub-array designating signal φ1, and an OR circuitOGab which receives the output signal of inverter OGaa and replacementinstruction signal φsp. In the bit line isolation control circuit shownin FIG. 13, when a normal memory sub-array is addressed, the outputsignal of inverter OGaa attains an L level. When a defective normal wordline is not addressed, replacement instruction signal φsp is at an Llevel, and therefore the output signal of OR circuit OGab attains an Llevel, which turns off bit line isolation gate BLIG0. Meanwhile, ifreplacement instruction signal φsp is activated and a spare word lineincluded in the spare array is used, the output signal of OR circuitOGab attains an H level, which turns on bit line isolation gate BLIG0.

However, the bit line isolation control circuit shown in FIG. 13 has adifferent circuit configuration from the control circuit provided forother bit line isolation gates and a different number of gate stages.(The OR circuit is formed by an NOR circuit and an inverter receivingthe output of the NOR circuit.) As a result, the gate delay isdifferent, the timing margin is reduced, and erroneous operation couldbe caused.

As shown in FIG. 11, in spare array SPX#0, by providing spare word lineswhich can replace defective normal word lines in normal memorysub-arrays MA#0-0 to MA#0-N, a spare word line included in a spare arrayincluded in this row block RBX#0 is not used if a defective normal wordline in normal memory sub-array M#1-0 is addressed. Therefore, in thiscase, the use of the bit line isolation control circuit shown in FIG. 14permits a defective normal word line to be accurately repaired byreplacement.

In FIG. 14, a 2-input NOR circuit OGc receiving sub-array designatingsignal φ1 is provided for bit line isolation gate BLIG0, and an NORcircuit OG receiving spare replacement instruction signal φsp0 andsub-array designating signal φ0 is provided for bit line isolation gateBLIG1. Spare replacement instruction signal φsp0 is driven into anactive state, H level, when a defective normal word line is addressed inany of normal sub-arrays MA#0-0 to MA#0-N. Sub-array designating signalφ0 is driven into an active state, H level, when normal memory sub-arrayMA#0-0 is addressed, while sub-array designating signal φ1 is driveninto an active state, H level, when normal memory sub-array MA#1-0 isaddressed.

When spare array SPX#0 provided corresponding to sub-array MA#0-0 isused, normal memory sub-array MA#1-0 will not be addressed. This isbecause a spare word line included in spare array SPX#0 is selected whena defective normal word line included in normal memory sub-arrays MA#0-0to MA#0-N is addressed. Also in this case, the output signal of NORcircuit OGc maintains an H level, the output signal of NOR circuit OGdattains an L level, and sense amplifier band SAB1 is connected to rowblock RBX#0 and disconnected from normal memory sub-array MA#1-0.Conversely, when normal memory sub-array MA#1-0 is addressed, the outputsignal of NOR circuit OGc attains an L level, row block RBX#0 isdisconnected from sense amplifier band SAB1, and normal memory sub-arrayMA#1-0 is connected to sense amplifier band SAB1. (The output signal ofNOR circuit OGd maintains an H level.)

The similar configuration is provided for the other row block RBX#1.Thus, a memory block including a spare array and a memory sub-arrayadjacent to this block will not be simultaneously addressed, so thatdefects can be accurately repaired.

FIG. 15 is a schematic diagram showing an example of replacement of adefective normal word line in the semiconductor memory device accordingto the fourth embodiment of the invention. In FIG. 15, spare array SPX#0includes spare word lines which can replace defective normal word linesin normal memory sub-arrays MA#0-0 to MA#0-N. Spare array SPX#1 includesspare word lines which can replace defective normal word lines includedin normal memory sub-arrays MA#1-0 to MA#1-N. Normal sub-arrays sharinga sense amplifier band have different values in address signal bit RAj.Thus, erroneous operation caused by access conflict (simultaneousselection of a normal/spare word line) can be prevented, so that defectscan be accurately repaired.

Fifth Embodiment

FIG. 16 is a diagram of a memory cell included in a semiconductor memorydevice. In FIG. 16, two memory cells MCa and MCb disposed correspondingto the crossing portions of word lines WLa and WLb and a bit line BL arerepresented. Memory cells MCa and MCb each include a capacitor MQ and anaccess transistor MT formed by an n-channel MOS transistor andresponsive to the signal potential of a corresponding word line (WLa orWLb) for connecting capacitor MQ to bit line BL. These memory cells MCaand MCb are both a dynamic type memory cell, to which a pair of bitlines BL and /BL is provided, and the potential difference generatedbetween bit lines BL and /BL is differentially amplified by a senseamplifier.

In the arrangement shown in FIG. 16, when word line WLa is driven into aselected state, the voltage level of non-selected word line WLb risesthrough the capacitive coupling by parasitic capacitance between wordlines WLa and WLb, access transistor MT included in memory cell MCb isweakly turned on, and the stored charge of capacitor MQ is transmittedonto bit line BL. When selected word line WLa makes a transition to anon-selected state, the capacitive coupling between word line WLa andbit line BL causes the voltage level of bit line BL to be lowered (whenbit line BL is driven to a ground voltage level), access transistor MTincluded in memory cell MCb connected to non-selected word line WLb isweakly turned on, and the stored charge of the capacitor is allowed toflow to bit line BL. Such a phenomenon of causing current leakage in amemory cell connected to a non-selected word line as another word lineis selected is called “disturb refresh”. If the charge holdingcharacteristic of a memory cell is poor, the stored data in the memorycell is lost before a refresh operation is performed at a prescribedcycle, and a soft-error is caused. In order to test such “disturbrefresh” characteristic, word lines are sequentially driven into aselected state and the charge holding characteristics of memory cellsare tested, in other words, a “disturb refresh test” is performed. Inthe “disturb refresh test”, in order to provide a prescribed number ofdisturbances to each memory cell, a word line is driven into a selectedstate a prescribed number of times.

If the storage capacity of a semiconductor memory device increases, thenumber of word lines increases accordingly, and time required for this“disturb refresh test” increases as well. In order to perform suchdisturb refresh test at a high speed, a larger number of word lines thanthe number of word lines selected at a time in a normal operation modeare simultaneously driven into a selected state in this disturb refreshtest. In this case, although depending upon the way to select a wordline, if the flexible redundancy scheme is employed, a spare word lineand a normal word line in one sub-array may be simultaneously driveninto a selected state to cause access conflict, the stored data in thememory cell is destroyed, and the disturb refresh test can no longer beperformed. The arrangement which can prevent a normal word line and aspare word line in one memory sub-array from being simultaneouslyselected even if a larger number of word lines than the number in thenormal operation mode are driven into a selected state in a disturbrefresh test will be now described.

FIG. 17 is a schematic diagram showing the arrangement of an arrayportion in the semiconductor memory device according to the fifthembodiment of the invention. In FIG. 17, the memory array includes twomemory mats B#0 and B#l. Memory mat B#0 includes normal memorysub-arrays MB#00-0 to MB#00-N and normal memory sub-arrays MB#01-0 toMB#01-N. Normal memory sub-arrays MB#00-0 to MB#00-N and normal memorysub-arrays MB#01-0 to MB#01-N are alternately disposed. Sense amplifierbands represented by shadowed regions are disposed between these normalmemory sub-arrays MB#00-0 to MB#00-N and MB#01-0 to MB#01-N. A sparearray SPX#00 including spare word lines is provided for normal sub-arrayMB#00-0, and a spare array SPX#01 including spare word lines is providedfor normal memory sub-array MB#01-N.

Normal memory sub-array MB#00-0 and spare array SPX#00 form a row block(sense amplifier block) RB#00, while normal memory sub-array MB#01-N andspare array SPX#01 form a row block RB#01. Normal memory sub-arrayMB#00-0 to MB#00-N form a memory block group B#00 which is addressedwhen row address bit RAj for example is 1, while normal memorysub-arrays MB#01-0 to MB#0 1-N form a memory block group B#01 selectedwhen row address signal bit RAj is for example 0.

Memory mat B#1 includes normal sub-arrays MB#10-0 to MB#10-N and normalmemory sub-arrays MB#11-0 to MB#11-N. Normal memory sub-arrays MB#10-0to MB#10-N and normal memory sub-arrays MB#11-0 to MB#11-N are providedalternately along the column direction. Sense amplifier bandsrepresented by shadowed regions are provided between these normal memorysub-arrays MB#10-0 to MB#10-N and normal memory sub-arrays MB#11-0 toMB#11-N. A spare array SPX#10 including spare word lines is provided fornormal memory sub-array MB#10-0, while a spare array SPX#11 is providedfor normal memory sub-array MB#11-N. Normal memory sub-array MB#10-0 andspare array SPX#10 form a row block (sense amplifier block) RB#10-0,while normal memory sub-array MB#11-N and spare array SPX#11 form a rowblock RB#11-N. Normal memory sub-arrays MB#10-0 to MB#10-N are includedin memory block group B#10, and normal memory sub-arrays MB#11-0 toMB#11-N are included in memory block group B#11.

In the array arrangement shown in FIG. 17, spare array SPX#00 providedin row block RB#00 includes spare word lines which can replace defectivenormal word lines in normal memory sub-arrays included in memory blockgroup B#10. Spare array SPX#01 included in row block RB#01 includesspare word lines which can replace defective normal word lines in normalmemory sub-arrays included in memory block group B#11. Spare arraySPX#10 included in row block RB#10-0 includes spare word lines which canreplace defective normal word lines in normal memory sub-arrays includedin memory block group B#00. Spare array SPX#11 included in row blockRB#11-N includes spare word lines which can replace defective normalword lines in normal memory sub-arrays included in memory block groupB#01. The operation will be now described.

Now assume that one normal memory sub-array is addressed by addresssignal bits RA0 to RAh as shown in FIG. 18A. A memory mat is addressedby row address signal bit RAi, and a memory block group is addressed byrow address signal bit RAj.

In the normal operation mode, these address signal bits RA0 to RAj areall valid, and one mat is addressed, in which one memory block group isaddressed and one normal sub-array is addressed in the addressed memoryblock group. If an addressed word line is a defective word line, a spareword line to replace the defective word line is included in a memory matdifferent from the selected memory mat. Therefore, the defective normalword line can be replaced without any problem (without problemsassociated with the sharing of a sense amplifier band).

Meanwhile, assume that row address signal bit RAj is in a degeneratedstate as shown in FIG. 18B in a test operation mode different from thenormal operation mode. Thus, one of memory mats B#0 and B#1 isaddressed, and one normal memory sub-array is addressed from each of twomemory block groups in the addressed memory mat. Since the two normalmemory sub-arrays are addressed in one memory mat, address signal bitsare allocated so that normal sub-arrays which do not share a senseamplifier band are addressed in the selecting operation. A correspondingspare word line used if the addressed normal word line is a defectivenormal word line is prepared in a non-selected memory mat. As a result,even if a plurality of (two) normal word lines are simultaneouslyaddressed in one memory mat, a spare word line and a normal word lineare prevented from being driven into a selected state at a time in rowblocks RB#00, RB#01, RB#10 and RB#11. In a non-selected memory mat, aspare word line in a row block is simply driven into a selected stateupon replacing a defective normal word line, and problems associatedwith sharing a sense amplifier band are not present.

If, for example, in the test operation mode, memory mat B#0 is addressedand a normal memory sub-array is selected from both memory block groupsB#00 and B#01, a corresponding spare word line is prepared in a sparearray SPX#10 included in row block RB#10 and/or in spare array SPX#11included in row block RB#11 in non-selected memory mat B#1. As a result,since the memory mat in which a spare word line is selected and thememory mat in which a normal word line is selected are different, anormal word line and a spare word line are prevented from being selectedat a time in one memory mat. By appropriately allocating address signalbits, two normal sub-arrays which do not share a sense amplifier bandcan be driven into a selected state in one memory mat. Note that if thenumber of memory mats is increased, the number of normal word linesdriven into a selected state at a time can be further increased.

FIG. 19 is a diagram showing a portion for changing the number ofsub-arrays to be selected depending upon the operation mode. In FIG. 19,there is provided a gate circuit (OR circuit) GT which receives addresssignal bit RAj and a test mode instruction signal TE. When test modeinstruction signal TE attains an active state of H level, memory blockgroup designating signal φB attains an active state, H level, regardlessof the value of row address signal bit RAj. As a result, in the testoperation mode, row address signal bit RAj can be pulled to adegenerated state, and normal sub-arrays can be addressed from twomemory block groups in one memory mat.

In order to address normal sub-arrays which do not share a senseamplifier band, the address of one memory block group and the address ofthe other memory block group need only be allocated in the oppositedirections. (If one memory block group is allocated with addresses 0 toN from the top to the bottom along the column direction, normalsub-arrays in the other memory group are sequentially allocated withaddresses 0 to N from the bottom to the top.)

As for the connection between a sense amplifier band and a spare arrayand the sensing operation in a non-selected memory mat, a spare decoderis constantly operated for comparison, and the comparison result isapplied to a spare array for each row block in the same manner as thatshown in FIG. 14. A sense amplifier control circuit provided for acorresponding row block has only to be activated when the output signalof the spare decoder is active. Thus, when a spare word line is used ina non-selected memory mat, a corresponding sense amplifier can beactivated.

For data accessing, the configuration the same as that shown in FIG. 4may be employed (in the disturb refresh test, data accessing is notperformed.)

Modification

FIG. 20 is a schematic diagram of a modification of the fifth embodimentaccording to the invention. In FIG. 20, similarly to the arrangementshown in FIG. 17, the memory array is divided into two memory mats B#0and B#1. In memory mat B#0, normal memory sub-arrays MB#00-0 to MB#00-Nbelonging to memory block group B#00 and normal memory sub-arraysMB#01-0 to MB#01-N included in memory block group B#01 are alternatelyprovided along the column direction. Spare array SPX#00 is provided fornormal memory sub-array MB#00-0, while spare array SPX#01 is providedfor normal memory sub-array MB#1-N. Spare array SPX#00 includes aplurality of spare word lines which can replace defective normal wordlines in normal memory sub-arrays belonging to memory block group B#00,while spare array SPX#01 includes spare word lines which can replacedefective normal word lines in normal memory sub-arrays belonging tomemory block group B#01.

In memory mat B#1, normal memory sub-arrays MB#10-0 to MB#10-N includedin memory block group B#10 and normal memory sub-arrays MB#11-0 toMB#11-N included in memory block group B#11 are alternately providedalong the column direction. Spare array SPX#10 is provided for normalmemory sub-array MB#10-0, while spare array SPX#11 is provided fornormal memory sub-array MB#11-N. Spare array SPX#10 includes a pluralityof spare word lines which can replace defective normal word lines innormal memory sub-arrays included in memory block group B#10, whilespare array SPX#11 includes a plurality of spare word lines which canreplace defective normal word lines in normal sub-arrays included inmemory block group B#11.

Also in the arrangement shown in FIG. 20, sense amplifier bandsrepresented by shadowed regions are provided between normal sub-arrays.

In this arrangement shown in FIG. 20, in the normal mode, one of memorymats B#0 and B#1 is selected, and one normal memory sub-array isselected in the selected memory mat. As a result, in the selected onememory mat, a normal word line is selected and a defective normal wordline is repaired by replacement in the same manner as that shown in FIG.11.

In the test mode, row address signal bit RAi, for example, is pulled toa degenerated state, and memory mats B#0 and B#1 are both addressed. Ineach of these memory mats B#0 and B#1, one normal sub-array is selected.In each of memory mats B#0 and B#1, normal sub-arrays included indifferent memory block groups are alternately provided, and normalsub-arrays sharing a sense amplifier band are included in differentmemory block groups. Therefore, in the test mode, normal memorysub-arrays sharing a sense amplifier are prevented from being addressedat the same time, in other words problems of sense amplifier conflictcan be prevented, so that a plurality of (two) normal word lines orspare word lines can be equivalently driven into a selected state fortesting operation. (In any of row blocks RB#00 to RB#11, a word line anda spare word line will not be driven into a selected state at the sametime.) Thus, the disturb refresh test can be performed at a high speed.

Note that in this fifth embodiment, the disturb refresh test has beendescribed. However, if a larger number of word lines than that in thenormal operation mode are driven into a selected state in the selfrefresh mode, a self refresh instruction signal can be used in place ofthe test mode instruction signal and the same effects are provided. Theconfiguration to degenerate address signal bit RAi (the address signalbit to address a memory mat) in the modification can be the sameconfiguration as that shown in FIG. 19.

As described above, according to the fifth embodiment of the invention,when a plurality of memory mats are provided, and a larger number ofnormal word lines than the number in the normal operation mode aredriven into a selected state in a particular operation mode such as thedisturb refresh test, a normal word line and a spare word line in onerow block are not simultaneously driven into a selected state, theadvantageous characteristic feature of the flexible redundancy scheme,in other words, the efficient use of spare decoders and spare word linesis not impaired and prescribed operation modes can be accuratelyimplemented.

Note that by increasing the number of memory mats in this modification,a larger number of normal word lines (4, 8) can be readily driven into aselected state at a time.

Sixth Embodiment

FIG. 21A is a schematic diagram showing a structure of a main part of asemiconductor memory device according to a sixth embodiment of theinvention. In FIG. 21A, the memory array is divided into a plurality ofmemory array blocks 2 a to 2 n. Memory array blocks 2 a to 2 n eachinclude a plurality of memory cells arranged in a matrix of rows andcolumns. A memory cell row is selected on a block basis. Row-relatedperipheral circuits 3 a to 3 n to drive memory cell rows in memory arrayblocks 2 a to 2 n into a selected state are provided for memory arrayblocks 2 a to 2 n, respectively. These row-related peripheral circuits 3a to 3 n which will be described in detail each include a decode circuit(which may include a predecoder) to decode an address signal and a wordline drive circuit to drive a memory cell row into a selected stateaccording to the output signal of the decode circuit.

Power supply switch circuits (SW) 4 a to 4 n driven into a selectedstate in response to selecting signals φBa to φBn are provided betweenrow-related peripheral circuits 3 a to 3 n and a main power supply line1. These power supply switch circuits 4 a to 4 n each cause a greatercurrent flow when driven into a selected state than when driven into anon-selected state. Main power supply line 1 is supplied with aprescribed voltage Vr. Voltage Vr may be any of a power supply voltageVcc, a ground voltage Vss and a high voltage Vpp or a combination ofthese voltages. A suitable voltage is selected as voltage Vr dependingupon the configuration of row-related peripheral circuits 3 a to 3 n.

In order to determine selection/non-selection of power switch circuits 4a to 4 n, a power supply block decoder 6 to generate selecting signalsφBa to φBn (generically represented as a control signal) based on anaddress signal AD and a self refresh mode instruction signal SR isprovided. Address signal AD is applied to row-related peripheralcircuits 3 a to 3 n as a memory cell row (word line) address.

Power supply block decoder 6 changes the number of power supply circuitsdriven into a selected state between a normal operation mode and a selfrefresh mode. Power supply block decoder 6 changes the selectingsequence of power supply switch circuits 4 a to 4 n between the selfrefresh mode and the normal mode. Based on these characteristics, if aspare word line is included in memory array blocks 2 a to 2 n, asemiconductor memory device operating with low current consumptionwithout increasing the accessing time can be implemented.

FIG. 21B is a diagram showing an example of row-related peripheralcircuits 3 a to 3 n shown in FIG. 21A. In FIG. 21B, one row-relatedperipheral circuit 3 is representatively shown.

In memory array block 2 (2 a to 2 n), memory cells MC are arranged in amatrix of rows and columns, and word lines WLa to WLm are provided formemory cells MC, respectively. A bit line pair BL, /BL is provided foreach column of memory cells, but only bit line BL is shown in FIG. 21.

Row-related peripheral circuit 3 includes repeating circuits provided.corresponding to word lines WLa to WLn. Herein, the repeating circuitshave the same configuration and the same function. A prescribed numberof repeating circuits among the plurality of repeating circuits areselected by an address signal.

In FIG. 21B, a repeating circuit includes an NAND-type decode circuit 11(11 a to 11 m), and a word line drive circuit 12 (12 a to 12 m) to drivea corresponding word line WL (WLa to WLm) into a selected state.

In a stand-by cycle, the output signals of NAND-type decode circuits 11a to 11 m are at an H level. As a result, in the stand-by cycle, inthese NAND-type decode circuits 11 a to 11 m, a sub-threshold leakagecurrent to the ground node is generated. Therefore, NAND-type decodecircuits 11 a to 11 m have each ground node coupled to a sub-ground line15 n. Sub-ground line 15 n is coupled to the ground node through a powersupply switch transistor 14 n. Power supply switch transistor 14 n turnson in response to control signal φBin.

Meanwhile, in inverter-type word line drive circuits 12 a to 12 m, theinput signals are at an H level in a stand-by cycle, and a sub-thresholdleakage current flows thereinto from the power supply node. As a result,the power supply nodes of these inverter-type word line drive circuits12 a to 12 m are coupled to a sub-power supply line 15 p. Sub-powersupply line 15 p is coupled to a voltage source node 16 through a powersupply switch transistor 14 p which conducts in response to a selectingsignal φBip. Voltage source node 16 is supplied with power supplyvoltage Vcc or high voltage Vpp. The voltage applied to voltage sourcenode 16 is appropriately determined depending upon the configuration ofthe repeating circuit.

NAND-type decode circuits 11 a to 11 m each have the other power supplynode coupled together to the main power supply line, and the groundnodes of inverter-type word line drive circuits 12 a to 12 m are coupledto the main ground line.

In a stand-by cycle, control signal φBin is set to an L level (groundvoltage level), while control signal φBip is set to an H level of thevoltage level of node 16. Thus, power supply switch transistors 14 n and14 p are turned off. These power supply switch transistors 14 n to 14 phave a large threshold voltage (high-Vth), and the sub-threshold leakcurrents are extremely small in the off state. Meanwhile, NAND-typedecode circuits 11 a to 11 m and word line drive circuits 12 a to 12 meach include a low-Vth MOS transistor as a component. As a result, thecurrent consumption in the repeating circuits, or the row-relatedperipheral circuits in a stand-by cycle can be reduced. Since theserepeating circuits operate at a high speed, the accessing time can bereduced as well.

In the correspondence between FIGS. 21A and 21B, power supply switchcircuits 4 a to 4 n correspond to power supply switch transistors 14 nto 14 p, while sub-power supply voltage source lines 5 a to 5 ncorrespond to sub-ground line 15 n and sub-voltage supply line 15 p. Theground node and voltage source node 16 correspond to main ground lineand main power supply line 1, respectively. Now, the specific manner toselect power supply switch circuits 4 a to 4 n will be described.

For the purpose of simplifying the description, a selecting operationwhen a spare line is not included will be described.

Hierarchical Power Supply Arrangement 1

FIG. 22 is a schematic diagram showing a main part of a semiconductormemory device according to the sixth embodiment of the presentinvention. In FIG. 22, a memory array is divided into eight memoryblocks MAB1 to MAB8. Memory blocks MAB1 to MAB8 each include a memoryblock 2 (2 a to 2 n) and a corresponding row-related peripheral circuit3 (3 a to 3 n) shown in FIG. 21A. Memory blocks MAB1 to MAB4 form oneglobal block GAB0, while memory blocks MAB5 to MAB8 form one globalblock GAB1.

Power supply switch circuits SW1 to SW8 are provided for memory blocksMAB1 to MAB8, respectively. These power supply switch circuits SW1 toSW8 couple sub-power supply lines provided corresponding to memoryblocks MAB1 to MAB8 and corresponding memory blocks.

In allocating addresses, three address signal bits RA1, AR2 and RA3 areused to address a block. Address bit RA1 specifies one of global blocksGAB0 and GAB1. A combination of address bits RA2 and RA3 specifies onememory block in global blocks GAB0 and GAB1. As a result, by these 3address signal bits RA1 to RA3, one memory block can be selected forselecting a memory cell row.

FIG. 23A illustrates the manner of selecting memory block and a powersupply switch circuit in a normal operation mode. In FIG. 23A, in thenormal operation mode, one of memory blocks MAB1 to MAB8 is selected andan addressed word line is driven into a selected state. In FIG. 23A, aword line WL in memory block MAB2 is driven into a selected state as anexample. When memory block MAB2 is selected, power supply switchcircuits SW1 to SW4 provided for global block GAB0 including memoryblock MAB2 are all driven into a selected state.

As shown in FIG. 23B, the set of power supply switch circuits SW1 to SW4or the set of power supply switch circuits SW5 to SW8 is selected byaddress signal bit RA1. As a result, by decoding 1-bit address signal,control signals φB1 to φB4 for the power supply switch circuits can bedriven into a selected state, so that a prescribed voltage can besupplied at a fast timing in an access cycle.

Meanwhile, in order to select memory block MAB2, 3 address signal bitsRA1 to RA3 should be decoded. Considering the timing skew of these 3address signal bits RA1 to RA3, a row-decoding operating for activatingmemory block address signal φB2 is performed. Thus, compared to the caseof decoding 1-bit address signal, the load of the output signal line ofthe decode circuit is greater in the case of decoding 3 address signalbits, and the skew prolongs the decoding time.

Therefore, in the normal operation mode, the power supply switchcircuits for a global block including selected memory block MAB2 aredriven into a selected state, so that a prescribed voltage can besupplied stably to the selected memory block at a fast timing after thestart of an active cycle in the normal operation mode, and the accessingtime can be prevented from increasing.

FIG. 24 is a diagram showing the manner to select a power switch circuitin a refresh mode. In FIG. 24, also in the refresh mode, a word line WLis selected in one memory block. Also in FIG. 24, memory block MAB2 isselected, in which word line WL to be refreshed is selected. In therefresh mode, only power supply switch circuit SW2 provided for theselected memory block MAB2 is driven into a selected state. The otherpower supply switch circuits SW1, SW3 to SW8 are maintained in anon-selected state. In the refresh mode, stored data is simplyrewritten, and data accessing is not performed. As a result, a highspeed accessing is not required, and therefore 3 refresh address signalbits QA1 to QA3 can be used to select this power supply switch circuitwithout any problem. By driving one power supply switch circuit into aselected state while maintaining the other power supply switch circuitsin a non-selected state, a current flowing through the power supplycircuit is reduced, the current consumption in the refresh mode can berestrained from increasing, in other words, the refresh mode withreduced current consumption can be implemented.

FIG. 25 is a schematic diagram showing a control portion in thesemiconductor memory device according to the sixth embodiment. In FIG.25, the semiconductor memory device includes an operation mode detectioncircuit 20 which receives an externally applied control signal CMD andgenerates an operation mode instruction signal, a refresh controlcircuit 23 which is activated in response to an activation of a selfrefresh mode instruction signal SR from refresh mode detection circuit22 to activate a timer 24 and generate a refresh cycle activation signalQACT at prescribed time intervals, a refresh address counter 25 whichperforms a counting operation in response to a count up instructionsignal φCUP from refresh control circuit 23 and generates a refreshaddress specifying a refresh row, a multiplexer 26 which selects one ofa refresh address signal QA from refresh address counter 25 and anexternally applied row address signal RA under the control of refreshcontrol circuit 23, and a row-related control circuit 27 which generatescontrol signals necessary for selecting a row according to refresh cycleactivation signal QACT from refresh control circuit 23 or arrayactivation signal RACT from an array activation detection circuitincluded in operation mode detection circuit 20.

Operation mode detection circuit 20 generates an instruction signalcorresponding to an operation mode designated according to externallyapplied control signal CMD. The externally applied control signal CMDmay be a command (a combination of states of a plurality of controlsignals) in a normal synchronous type semiconductor memory device, ormay be a row address strobe signal /RAS, a column address strobe signal/CAS, a write enable signal /WE and a chip select signal /CS as in astandard DRAM (Dynamic Random Access Memory). The external controlsignal applied to operation mode detection circuit 20 may beappropriately determined depending upon the configuration of thesemiconductor memory device.

Refresh control circuit 23 drives refresh cycle activation signal QACTinto an H level, active state for a prescribed time period at prescribedtime intervals according to a count up signal from timer 24 when selfrefresh mode instruction signal SR is activated. Row-related controlcircuit 27 generates control signals necessary for selecting a row whenone of activation signals QACT and RACT is activated. In FIG. 25,row-related control circuit 27 generates a word line driving signal φWLwhich gives a timing for driving a word line into a selected state.During the activation period of these activation signals QACT and RACT,in a memory block addressed by an address signal, a row (word line) ismaintained in a selected state. The activation period of theseactivation signals QACT and RACT defines one memory cycle (for aselected memory block).

Timer 24 responds to a self refresh instruction from refresh controlcircuit 23 to generate a refresh request signal at prescribed timeintervals for application to refresh control circuit 23. Refresh addresscounter 25 increments or decrements the count value by 1 according tocount up instruction signal φCUP applied at the end of this memorycycle. Multiplexer 26 selects refresh address QA from refresh addresscounter 25 in the self refresh mode according to a switch controlcircuit φMUX from refresh control circuit 23 and selects externallyapplied row address signal RA in the normal mode. Address signal AD frommultiplexer 26 is applied to a row-related peripheral circuit in eachmemory block. In the address signal, address signal bits QA1 to QA3 orRA1 are applied to a power supply block decoder (see FIG. 21A). Sincethe address signal bits are transmitted through the same bus lines frommultiplexer 26, 3 address signal bits are applied to the power supplyblock decoder through the same address signal lines, and then theseaddress bits are supplied in different paths within power supply blockdecoder 6.

FIG. 26 is a diagram showing a structure of power supply block decoder 6shown in FIG. 21A. In FIG. 26, a portion to generate one power supplyblock selecting signal φBi (i=1 to 8) is shown. In FIG. 26, power supplyblock decoder 6 includes an inverter circuit 6 a which inverts selfrefresh instruction signal SR, an AND circuit 6 b which receivesprescribed 3 address signal bits among address signal bits QA1 to QA3and /QA1 to /QA3 in the refresh mode, an AND circuit 6 c which receivesthe output signal /SR of inverter circuit 6 a and address bit RA1 or/RA1, an AND circuit 6 d which receives self refresh mode instructionsignal SR and the output signal of AND circuit 6 b, and an AND circuit 6e which receives the output signals of AND circuits 6 c and 6 d andgenerates power supply block selecting signal φBi. AND circuit 6 b issupplied with address signal bits corresponding to the address of amemory block provided corresponding to power supply block selectingsignal φBi. Similarly to NAND circuit 6 c, address bit RA1 or /RA1 tospecify a global block including a memory block corresponding to powersupply block selecting signal φBi is applied.

In the self refresh mode, self refresh mode instruction signal SR is atan H level, signal /SR from inverter circuit 6 a is at an L level, andNAND circuit 6 c outputs an H level signal regardless of the states ofaddress bits RA1 and /RA1. Meanwhile, NAND circuit 6 a operates as aninverter to invert the output signal of AND circuit 6 b. Therefore, inthe self refresh mode, power supply block selecting signal φBi isgenerated according to address bits QA1 to QA3 and /QA1 to /QA3.

Meanwhile, in the normal operation mode, self refresh mode instructionsignal SR is at an L level and the output signal /SR of inverter circuit6 a is an H level. In this state, the output signal of NAND circuit 6 dattains an H level, NAND circuit 6 c operates as an inverter, and powersupply block selecting signal φBi is generated according to address bitRA1 or /RA1. Thus, in the normal mode, power supply block selectingsignals φBi for a global block including a selected memory block (amemory block including a selected row) are activated. Meanwhile, in theself refresh mode, power supply block selecting signal φBi for a powersupply switch circuit provided corresponding to a memory block to berefreshed is driven into a selected state.

FIG. 27 is a diagram showing a structure of a portion to generate powersupply block selecting signal φB2 to power supply switch circuit SW2.For power supply block selecting signal φB2, AND circuit 6 b receivesaddress bits /QA1, /QA2 and QA3, and NAND circuit 6 c receives addressbit /RA1. The address (QA1, QA2, QA3) of a memory block having powersupply switch circuit SW2 is (0, 0, 1). Therefore, when memory blockMAB2 is addressed, the output signal of AND circuit 6 b attains an Hlevel. Meanwhile, in the normal mode, address bit /RA1 attains an Hlevel (“1”), and power supply block selecting signals φB1 to φB4 topower supply switch circuits SW1 to SW4 provided corresponding to globalblock GB0 including memory block MAB2 are driven into an H level,selected state. By changing the number of decoded bits depending uponthe operation mode, the number of power supply switch circuits driveninto a selected state can be changed between the normal mode and theself refresh mode.

If the number of memory blocks are 8, there are two global blocks, a1-bit address signal is decoded in the normal mode, while a 3-bitaddress signal is decoded in the self refresh mode. However, the numberof address signal bits used in the normal mode and self refresh mode canbe appropriately determined depending upon the number of memory blocksand global blocks. The number of address signal bits validated in thenormal mode has only to be smaller than the number of address signalbits decoded in the self refresh mode.

Modification

FIG. 28 is a schematic diagram showing a modification of hierarchicalpower supply arrangement 1 according to the sixth embodiment of theinvention.

In the configuration shown in FIG. 28, refresh address QA from therefresh address counter and externally applied row address signal RA areapplied to multiplexer 26. The row-related peripheral circuit issupplied with an internal row address signal from multiplexer 26.Meanwhile, address bits QA1 to QA3 from refresh address counter 25 andinternal row address bit RA1 from multiplexer 26 are applied to a powersupply block decode circuit. In this configuration, refresh address bitsQA1 to QA3 are directly applied to the power block decode circuit fromrefresh address counter 25. Since the address bits do not pass throughmultiplexer 26, the influence of gate delay (signal propagation delay)in multiplexer 26 is eliminated in the self refresh mode, and a decodingoperation can be performed at a fast timing.

As described above, according to hierarchical power supply arrangement1, the number of address bits used for selecting a power supply block ischanged between the normal mode and refresh mode, the accessing time inthe normal mode is not increased, and the current consumption can bereduced in the refresh mode.

Modification 2

FIG. 29 is a schematic diagram showing a modification 2 of hierarchicalpower supply arrangement 1. In FIG. 29, the configuration of a part ofrow-related control circuit 27 shown in FIG. 25 is shown. In FIG. 29,row-related control circuit 27 includes an OR circuit 30 which receivesactivation signals QACT and RACT, a word line activation signalgeneration circuit 31 which is responsive to a rising of the outputsignal of OR circuit 30 for driving a word line activation signal φRXinto an active state, a delay circuit 32 which delays word lineactivation signal φRX from word line activation signal generationcircuit 31 by a prescribed time period, and a selecting circuit 33 whichselects one of the output signal of delay circuit 32 and signal φRX fromword line activation signal generation circuit 31 according to selfrefresh mode instruction signals SR and /SR to generate a word linedriving signal φWL. Selecting circuit 33 includes a CMOS transmissiongate 33 a which conducts to pass the output signal of delay circuit 32in response to an activation of self refresh mode instruction signal SR,and a CMOS transmission gate 33 b which conducts to pass word lineactivation signal φRX from word line activation signal generationcircuit 31 in response to an inactivation of self refresh modeinstruction signal SR.

The operation of row-related control circuit 27 will be described withreference to the signal waveform diagram in FIG. 30.

In a normal mode, array activation signal RACT is driven into an activestate according to a memory cycle start instruction signal (or an activecommand). When array activation signal RACT is activated, the outputsignal of OR circuit 30 is activated, and word line activation signalgeneration circuit 31 generates word line activation signal φRX at aprescribed timing. In the normal mode, CMOS transmission gate 33 bconducts, and CMOS transmission gate 33 a is in a non-conductive state.As a result, word line driving signal φWL is generated according to wordline activation signal φRX. When one active cycle completes, arrayactivation signal RACT falls to an L level non-selected state, word lineactivation signal φRX is inactivated accordingly, and a selected wordline is driven into a non-selected state.

In the self refresh mode, refresh activation signal QACT is activated.Word line activation signal generation circuit 31 responds to theactivation of refresh activation signal QACT to drive word lineactivation signal φRX into an active state. In the self refresh mode,CMOS transmission gate 33 a conducts, while CMOS transmission gate 33 bis in a non-conductive state. As a result, word line driving signal φWLis driven into an active state according to a delayed word lineactivation signal from delay circuit 32.

By delaying the activation timing of word line driving signal φWL in theself refresh mode, after a power supply switch circuit is selected and aprescribed supply voltage to a memory block to be refreshed isstabilized, a word line is selected, so that a decoding operation can beperformed accurately to drive the addressed word line (refresh row) intoa selected state. As shown in the waveforms in FIG. 30, delay circuit 32is a rising delay circuit, and word line driving signal φWL may beinactivated in response to an inactivation of refresh activation signalQACT. Even if a word line is driven into a selected/non-selected statewith a delay to refresh activation signal QACT, the sense amplifier isactivated/inactivated according to this word line driving signal φWL,and there will be no problem. The problem of so-called RAS prechargetime is not caused particularly in the self refresh mode. In the selfrefresh mode, the refresh interval is, for example, as long as 16 μs,the RAS precharge time period can be sufficiently secured, even if suchdelay circuit 32 is used.

FIG. 31 is a diagram showing a part of a row-related peripheral circuitoperating according to word line driving signal φWL shown in FIG. 29. InFIG. 31, the configuration of a repeating circuit for one word line WLis shown. In FIG. 31, the repeating circuit includes an NAND-type decodecircuit 41 which receives address bits (a predecode signal) Xi, Xj andXk, a decode transistor 42 which is formed by an n-channel MOStransistor and selectively transmits the output of NAND-type decodecircuit 41 onto a node 41 according to an address bit (predecode signal)X1, a p-channel MOS transistor 43 which responds to a reset signal RSTto precharge a node 49 to high voltage Vpp level, a p-channel MOStransistor 44 which transmits a signal SDX from a word line decodesignal generation circuit 40 onto a word line WX when the signal on node49 is at an L level, an n-channel MOS transistor 45 which conducts whenthe signal on node 49 is at an H level to discharge word line WL to aground voltage level, a p-channel MOS transistor 46 which conducts whenthe signal on word line WL is at an L level to maintain node 49 at highvoltage Vpp level, and an n-channel MOS transistor 47 which conductswhen signal /SDX from word line decode signal generation circuit 40 isat an H level to discharge word line WL to the ground voltage level.

Herein, the decode circuit is formed by NAND-type decode circuit 41 anddecode transistor 42. The word line drive circuit is formed by MOStransistors 44 to 47.

Word line decode signal generation circuit 40 is activated in responseto an activation of word line driving signal φWL, to generate signalsSDX and /SDX according to an address bit (predecode signal) Xm. SignalSDX changes between high voltage Vpp and ground voltage Vss. Signal /SDXchanges between power supply voltage Vcc and the ground voltage.

In a stand-by state, address bits Xi, Xj and Xk are all at an L level.As a result, in NAND-type decode circuit 41, a sub-threshold leakagecurrent flows to the ground potential, the ground node of NAND-typedecode circuit 41 is connected to the main ground line through a MOStransistor 48. MOS transistor 48 receives power supply block selecting(specifying) signal φBi at its gate. The operation will be now brieflydescribed.

In a stand-by state, address bits Xi, Xj and Xk are all at an L level,and the output signal of NAND-type decode circuit 41 is at an H levelequal to the power supply voltage Vcc level. MOS transistor 48 is in anoff state, because power supply block selecting signal φBi is at an Llevel. In a stand-by state, word line decode signal generation circuit40 holds signal SDX at an L level equal to the ground voltage level, andsignal /SDX at an H level. Node 49 is held at the high voltage Vpp levelby reset signal RST through MOS transistor 43. In this state, word lineWL is held at the ground voltage level by MOS transistors 45 and 47.

When an active cycle is started, power supply block selecting signal φBiattains an H level when selected, and NAND-type decode circuit 41receives power supply voltage Vcc and ground voltage Vss as bothoperation power supply voltages to perform a decoding operation. Whenaddress bits Xi, Xj, Xk and Xl are all at an H level, node 49 isdischarged to the ground voltage level by the function of NAND-typedecode circuit 41. (MOS transistor 49 for reset is in an off state.) MOStransistor 46 has a small current driving capability, and therefore node49 is surely discharged to the ground voltage level by NAND-type decodecircuit 41 and decode transistor 42. When the voltage level on node 49becomes an L level, MOS transistor 45 attains an off state. MOStransistor 44 shifts to an off state, because signal SDX is at an Llevel and the gate and source potentials of the transistor 44 are equal.

Word line decode signal generation circuit 40 is responsive to anactivation of word line driving signal φWL for operating to drivesignals SDX and /SDX to an H level/L level according to address bit Xm.When address bit Xm is at an H level, signal SDX is driven into the highvoltage Vpp level, and signal /SDX is discharged to the ground voltagelevel. Therefore, at this time, word line WL is driven into the highvoltage Vpp level through MOS transistor 44. Meanwhile, when address bitXm is at an L level, signal SDX attains an L level and signal /SDXattains an H level. As a result, p-channel MOS transistor 44 maintainsan off state. When MOS transistors 44 and 45 both attain an off state,MOS transistor 47 is turned on by signal /SDX and word line WL is surelymaintained at the ground voltage level.

In the case of the repeating circuit shown in FIG. 31, one row decodecircuit is provided for two word lines WL. One of the two word lines isselected by signals SDX and /SDX. If address signal bit Xm applied toword line decode signal generation circuit 40 is replaced by two-bitaddress, one row decode circuit is provided for four word lines.

Thus, in the case of the configuration of the repeating circuit shown inFIG. 31, in the normal mode, word line driving signal φWL is driven intoan active state at a fast timing, and word line WL is driven into anactive state at a fast timing accordingly. Meanwhile, in the selfrefresh mode, the activation of word line driving signal φWL is delayedbehind the activation of power supply block selecting signal φBi. Powersupply block selecting signal φBi is driven into an active state at arelatively delayed timing (in order to fully decode a power supply blockaddress signal) in the self refresh mode. After the voltage level of theground node of NAND-type decode circuit 41 surely reaches. the groundvoltage level, signals SDX and /SDX from word line decode signalgeneration circuit 40 are driven into a specified state. Thus, in theself refresh mode, a decoding operation can be surely performed totransmit high voltage Vpp or ground voltage Vss onto selected word lineWL.

In the configuration shown in FIG. 31, as a so-called hierarchical powersupply arrangement, a sub-ground line is connected to NAND-type decodecircuit 41. If word line decode signal generation circuit 40 is providedfor each of memory blocks, a power supply switch circuit may be providedfor each memory block for a signal line supplying high voltage Vpp, andhigh voltage Vpp may be supplied in the above described manner. In wordline decode signal generation circuit 40, a leakage current from highvoltage Vpp can be prevented from flowing by a sub-threshold leakagecurrent and current can be prevented from being consumed. In thisconfiguration, the power supply nodes (sources) of MOS transistors 43and 46 need only be coupled to a sub-high voltage supply line common toword line decode signal generation circuit 40.

According to the configuration of modification 2 as described above, inaddition to the previously described effects, a word line can be drivenafter the voltage at the operation voltage supply node is stabilized, sothat a decoding operation can be surely performed and an addressed wordline can be surely driven into a selected state. Note that if highvoltage Vpp is provided in a hierarchical power supply arrangement, aword line can be driven after high voltage Vpp is stabilized.

Hierarchical Power Supply Arrangement 2

FIGS. 32A and 32B are diagrams showing the selected state of the powersupply circuit in hierarchical power supply arrangement 2 according tothe sixth embodiment of the invention. As shown in FIG. 32A, a word lineWL is driven into a selected state in a single memory block in a normalmode. In this case, a power supply switch circuit provided for a globalblock including a selected memory block is driven into a selected state.In FIG. 32A, word line WL is selected in memory block MAB2, and powersupply switch circuits SW1 to SW4 for global array block GAB0 includingmemory block MAB2 are driven into a selected. This is the same as theoperation of the previously described power supply arrangement 1 in thenormal mode.

As shown in FIG. 32B, in a refresh mode, one memory block is selected ineach of global array blocks GAB0 and GAB1 for refreshing. In this case,power supply switch circuits SW2 and SW6 provided for memory blocks MAB2and MAB6 are driven into a selected state. Address bits are allocatedsimilarly to the allocation of the address bits shown in FIG. 22. Inthis case, in a self-refresh mode, an address bit QA1 to specify aglobal block is degenerated (ignored). Therefore, a power supply blockselecting signal is generated according to address bits QA2 and QA3.

FIG. 33 is a schematic diagram showing a structure of a power supplyblock decode circuit. Since the power supply block decode circuit shownin FIG. 33 has the same configuration as shown in FIG. 26, except forthat an AND circuit 6 f to decode refresh address bits receives aprescribed set among refresh address bits QA2, QA3, /QA2 and /QA3, thecorresponding portions are denoted with the same reference charactersand the detailed description is not provided.

In power supply block decode circuit 6 shown in FIG. 33, refresh addressbits QA1 and /QA1 are not used. Therefore, one memory block is selectedin each of global blocks GAB0 and GAB1.

FIG. 34 is a diagram showing a structure of the portion to generate acontrol signal (power supply block selecting signal) φB2 to power supplyswitch circuit SW2 provided for memory block MAB2. In FIG. 34, in thepower supply block decode circuit, refresh address bits /QA2 and QA3 areapplied to AND circuit 6 f. Memory block MAB2 is selected when refreshaddress bits (QA2 and QA3) are (0, 1). Therefore, when memory block MAB2is addressed, the output signal of AND circuit 6 f attains an H level,and power supply block selecting signal φB2 is driven into an H level,active state. In the power supply block decode circuit, address bit QA1is not used, therefore memory block MAB6 is also selected in globalblock GAB1, and corresponding power supply switch SW6 is driven into aselected state.

In this hierarchical power supply arrangement 2, as shown in FIG. 35,word line driving signal φWL is applied to a row-related selectingcircuit 50 included in a row-related peripheral circuit 3. A prescribedvoltage Vr is applied to row-related selecting circuit through a powersupply switch circuit SW. Row-related selecting circuit 50 drives any ofword lines WL0 to WLm into a selected state in response to an addresssignal Ad when selected. Power supply switch circuit SW is driven into aselected state in response to a power supply block selecting signal φBi.Row-related selecting circuit 50 includes a word line decode signalgenerating circuit 40 shown in FIG. 31. Word line driving signal φWL isgenerated by a control circuit shown in FIG. 29. Therefore, word linedriving signal φWL applied to row-related selecting circuit 50 has itsactivation timing in a self-refresh mode delayed behind the activationtiming in a normal operation mode. Thus, power supply switch circuit SWis driven into a selected state, and after stable voltage Vr is suppliedto row-related selecting circuit 50, row-related selecting circuit 50performs a word line selecting operation. Thus, the selected word linecan be stably driven into a selected state.

According to this hierarchical power supply arrangement 2, if a largernumber of word lines than those in the normal mode are driven into aselected state in the refresh mode, a power supply switch circuit in aglobal block is driven into a selected State in the normal mode, whilein the self-refresh mode, only the power supply switch circuit for aselected memory block is driven into a selected state, so that the powerconsumption in the refresh mode can be reduced without increasing theaccessing time. The word line driving timing can be delayed in theself-refresh mode to accurately perform a word line selecting operation.

There are eight memory blocks in this hierarchical power supplyarrangement 2, but the number of memory blocks may be as desired, andthe number of global blocks is also arbitrary. In the self-refresh mode,two word lines are selected, but the number of rows refreshedsimultaneously is also arbitrary, and the number of refresh address bitshas only to be adjusted depending upon the number of rows to besimultaneously refreshed.

Hierarchical Power Supply Arrangement 3

FIG. 36 is a schematic diagram showing the configuration of hierarchicalpower supply arrangement 3 according to the sixth embodiment of thepresent invention. In FIG. 36, the configuration of the portion tocontrol this hierarchical power supply circuit is shown.

In FIG. 36, a power supply block selecting signal generating portionincludes a power supply block decoder 6 which decodes a refresh addressoutput from refresh address counter 25 and latches the result ofdecoding in advance by one cycle, and outputs the latched result in thepresent refresh cycle. Refresh address counter 25 counts in response toa count up instruction signal CUP activated in a refresh cycle, andholds the count value. The count value output from refresh addresscounter 25 is applied to register 65. Register 65 responds to aninstruction signal φCUP activated at the end of the refresh cycle totake and output the output count value of refresh address counter 25. Anaddress signal output from register 65 is applied to a multiplexer (MUX)26 as a refresh address signal QA.

Power supply block decoder 6 includes a power supply block decodecircuit 60 which decodes the output count of refresh address counter 25,a latch 61 which responds to an activation of count up instructionsignal CUP to latch the output signal of power supply block decodecircuit 60, a latch 62 which responds to refresh cycle activation signalQACT to take and output the data latched by latch 61, and a selector 63which selects one of the output signal of latch 62 and address bit RA1from multiplexer 26 according to self refresh mode instruction signal SRto output power supply block selecting signals φB1 to φB8. Herein, thememory array is divided into eight memory blocks MAB1 to MAB8, and aglobal block or four memory array blocks are selected according to thisrow address bit RA1. The operations of the control signal generationportion shown in FIG. 36 will be now described with reference to thesignal waveform diagram in FIG. 37.

In a self-refresh mode, when refresh cycle activation signal QACT is inan inactive state, latch 61 latches power supply block selecting signalφBi(N−1) generated by power supply block decode circuit 60 in theprevious cycle (N−1). Latch 62 also latches power supply block signalφBi(N−1). Selector 63 selects the output signal of latch 62 in responseto self-refresh mode instruction signal SR.

When refresh cycle activation signal QACT is activated, latch 62 outputsthe latched data, and power supply block selecting signals φBi is driveninto a selected/non-selected state based on the result of decoding inthe previous memory cycle (N−1). In this cycle (N), register 65generates a refresh address taken in the previous cycle. Therefore, inthis cycle (N), the selecting control of the power supply switch circuitand refresh operation are performed based on power supply blockselecting signal φBi(N−1) and refresh address QA (N−1) decoded in theprevious cycle. In the previous cycle, the decoding operation ofgenerating the power supply block selecting signal is completed, andwhen refresh cycle activation signal QACT is activated, power supplyblock selecting signal φBi(N−1) is immediately made definite. As aresult, in the refresh cycle, the word line selecting timing does nothave to be delayed, and the refresh operation may be performed at fasttiming. The word line selecting timing does not have to be changedbetween the normal mode and refresh mode, and the control in selectingword lines is easily made.

In response to an activation of this refresh cycle activation signalQACT, count up instruction signal CUP is activated at a prescribedtiming. In response to the activation of count up instruction signalCUP, refresh address counter 25 performs a count up operation, and thecount value is incremented or decrement by 1. Power supply block decodecircuit 60 decodes a refresh address from refresh address counter 25,and generates a power supply selecting signal based on the result ofdecoding. Latch 61 takes the output signal of power supply block decodecircuit 60 in response to count up instruction signal CUP and enters alatching state in response to an inactivation of count up instructionsignal CUP. During this period, a refresh operation is performedaccording to refresh address QA (N−1) generated in the previous cycle.

When refresh cycle activation signal QACT is inactivated, latch 62 takesa latched signal from latch 61 and drives the output signal into aninactive state. Thus, power supply block selecting signals φB1 to φB8are all driven into an inactive state. In response to the activation ofrefresh cycle activation signal QACT, count up instruction signal φCUPis activated, and register 65 takes the count value output from refreshaddress counter 25. Thus, refresh address QA changes by 1.

When refresh cycle activation QACT is then activated again, latch 62outputs the latched power supply block selecting signal, and powersupply block selecting signals φB1 to φB8 are driven into aselected/non-selected state according to power supply block selectingsignal φBi(N) obtained in the previous cycle (N). In this cycle (N+1),register 65 outputs the refresh address taken at the end of the previouscycle, and applies the address to the row-related circuits. According torefresh address QA(N) and power supply block selecting signal φBi(N)generated in the previous cycle, a refresh operation is executed.

In the activation period of this refresh cycle activation signal QACT,count up instruction signal CUP is activated, refresh address counter 25performs a counting operation, and the count value is updated. Powersupply block decode circuit 60 performs a decoding operation again togenerate power supply block selecting signal φBi(N+1), and latch 61latches power supply block selecting signal φBi(N+1) from power supplyblock decode circuit 60.

When refresh cycle activation signal QACT is inactivated, latch 62 onceagain takes the output signal of latch 61, and has the content thereofupdated to power supply block selecting signal φBi(N+1). In response tothe inactivation of refresh cycle activation signal QACT, latch 62 againdrives output signal φBi(N) into a non-selected state. In response tothe inactivation of refresh cycle activation signal QACT, count upinstruction signal φCUP is activated, and register 65 takes the outputcount value of refresh address counter 25 and updates the refreshaddress. Each time refresh cycle activation QACT is activated atprescribed time intervals, the above-described operation is repeated.

In a refresh operation, a refresh address is generated according to thecounting operation of refresh address counter 25. Therefore, in eachrefresh cycle, the next refresh address can be known, and therefore apower supply block selecting signal may be generated in advance bydecoding the refresh address in the previous cycle. Thus, at the startof a refresh cycle, a decoding operation of selecting a power supplyblock is not necessary, and therefore a word line corresponding to arefresh row can be driven into a selected state at a faster timing.

FIG. 38 is a diagram showing an example of power supply block decoder 6.In FIG. 38, power supply block decode circuit 60 includes an NAND-typedecode circuit 60 a which receives prescribed refresh address bits QAi,and /QAi. The combination of refresh address bits QAi, and /QAi appliedto NAND-type decode circuit 60 a is determined by the address of amemory block corresponding to the power supply switch circuit controlledby power supply block selecting signal φBi.

Latch 61 includes a transfer gate 61 a which conducts to pass the outputsignal of NAND-type decode circuit 60 a when count up instruction signalCUP is activated (at an H level), and inverters 61 b and 61 c which forma latch circuit to latch a signal applied through transfer gate 61 a.Inverters 61 b and 61 c are disposed in an anti-parallel arrangement andhave their inputs and outputs cross-coupled to form a so-called inverterlatch.

Latch 62 includes a transfer gate 62 a which conducts to pass the outputsignal of latch 61 when complimentary refresh cycle activation signal/QACT is activated, inverters 62 b and 62 c which form a latch circuitto latch a signal applied through transfer gate 62 a, and AND circuit 62d which is activated in response to an activation of refresh cycleactivation signal QACT to generate power supply block selecting signalφBi. Inverters 62 b and 62 c form a so-called inverter latch.

In the configuration shown in FIG. 38, power supply block decode circuit60 decodes refresh address bits QAi and /QAi from the refresh addresscounter and outputs a signal representing the result of decoding. Inlatch 61, transfer gate 61 a conducts when count up instruction signalCUP is activated and passes a power supply block selecting signal newlygenerated by the activation of count up instruction signal CUP, andinverters 61 b and 61 c latch this newly generated power supply blocksignal. During the refresh cycle period, complimentary refresh cycleactivation signal /QACT is in an inactive state, and the content latchedby latch 62 does not change regardless of change in the output signal oflatch 61.

During the refresh cycle period, AND circuit 62 d operates as a bufferto output the power supply block selecting signal latched by inverters62 b and 62 c. When the refresh cycle completes and refresh cycleactivation signal QACT attains an L level, inactive state, AND circuit62 d is disabled, and power supply block selecting φBi attains an Llevel, inactive state. Thus, the power supply switch circuits all attaina non-selected state, which reduces the power consumption. Meanwhile,when complimentary refresh cycle activation signal /QACT attains an Hlevel, active state, transfer gate 62 a conducts to take the signallatched by latch 61 and latches a new power supply block selectingsignal.

Without adversely affecting the refresh cycle operation in the presentcycle, a power supply block selecting signal is generated and latched bydecoding a refresh address for the next cycle.

FIG. 39 is a diagram showing an example of a 1-bit register circuit inregister 65 shown in FIG. 36. In FIG. 39, register 60 includes atransfer gate 65 a which conducts to pass a count bit from the refreshaddress counter when count up instruction signal φCUP is activated,inverters 65 b and 65 c which form a latch circuit to latch a signalapplied through transfer gate 65 a, an inverter 65 d which inverts theoutput signal of inverter 65 b, and an AND circuit 65 e which is enabledto generate refresh address bit QAi according to the output signal ofinverter 65 d when refresh cycle activation signal QACT is activated.

In the configuration of register 65 shown in FIG. 39, the refreshaddress bit latched by inverters 65 b and 65 c is updated when count upinstruction signal φCUP is activated. When refresh cycle activationsignal QACT is activated, refresh address bit QAi to be used in thepresent cycle is generated.

When multiplexer 26 is provided in the stage preceding the row addressbuffer/latch, this AND circuit 65 e is not necessary. The row addressbuffer/latch functions to maintain the internal row address signal bitsin an active state in a stand-by cycle.

FIG. 40 is a schematic diagram representing how count up instructionsignals CUP and φCUP are generated. In FIG. 40, the count up instructionsignal generation portion includes a delay circuit 67 which delaysrefresh cycle activation signal QACT by a prescribed time period, aone-shot pulse generation circuit 68 which generates a one-shot pulsesignal in response to a rising of the output signal of delay circuit 67,an inverter circuit 69 which inverts refresh cycle activation signalQACT, and a one-shot pulse generation circuit 70 which generates aone-shot pulse signal in response to a rising of the output signal ofinverter circuit 69. Count up instruction signal CUP is output fromone-shot pulse generation circuit 68, and count up instruction signalφCUP is output from one-shot pulse generation circuit 70. By setting thedelay time by delay circuit 67 to an appropriate value, a count upoperation can be performed by the refresh address counter within therefresh cycle period at an appropriate timing. The activation periods ofcount up instruction signals CUP and φCUP may be determined suitablydepending upon the latching ability of each circuit.

Note that this count up instruction signal generation circuit has onlyto be included in refresh instruction control circuit 23 in FIG. 25.

In hierarchical power supply configuration 3, power supply blockselecting signal φBi is set to an H level when selected. However, thelogical level of the power supply block selecting signals φBi in theselected state may be appropriately determined depending upon thevoltage level of the voltage supply lines applied. For example, if thepower supply switch circuit is provided between a main ground line and asub ground line, power supply block selecting signal φBi attains an Hlevel when selected, while if the power supply switch circuit isprovided between a main power supply line and a sub power supply line,power supply block selecting signal φBi attains an L level whenselected.

Note that in the configuration shown in FIG. 36, in a normal mode,selector 63 selects row address signal bit RA1 from multiplexer 26 inresponse to self-refresh mode instruction signal SR. Therefore, a globalblock is selected according to this row address signal bit RA1.

As described above, according to hierarchical power supply arrangement3, in the self-refresh mode, a power supply block selecting signal to beused in the next cycle is generated by incrementing and decoding thecount value of the refresh address counter in the present cycle followedby latching the result of decoding. Therefore, the decoding operation ofthe power supply block selecting signal has been completed at the startof the next cycle, and the state of power supply block selecting signalφBi can be set at a high speed in the next cycle, so that a word linecan be driven into a selected state at a faster timing in a refreshcycle. As a result, the activation timing for a word line does not haveto be changed between the refresh mode and the normal mode, andtherefore the configuration of the word line driving portion can besimplified.

Seventh Embodiment

Hierarchical Power Supply Arrangement 1

FIG. 41 is a schematic diagram showing the configuration of an arrayportion in a semiconductor memory device according to a seventhembodiment of the present invention. In FIG. 41, a memory mat is dividedinto eight memory blocks MAB1 to MAB8. Memory blocks MAB2 to MAB8include normal memory blocks NMAB2 to NMAB8 including normal memorycells, respectively. Memory block MAB1 includes a normal memory blockNMAB1 and a spare block SPB including a spare element to repair adefective cell. Memory block MAB1 corresponds to a block RBX# formed bya normal memory sub array and a spare array shown in FIG. 11.

Switch circuits SW1 to SW8 are provided corresponding to memory blocksMAB1 to MAB8. Switch circuits SW1 to SW8 are driven into a selectedstate according to power supply block selecting signals φB1 to φB8similarly to the forgoing sixth embodiment. Spare block SPB for memoryblock MAB1 is shared among normal memory blocks NMAB2 to NMAB8, and canrepair a defective cell (defective row) in any of the normal memoryblocks by replacing the defective cell. Block address bits RA1 to RA3and QA1 to QA3 for memory blocks MAB1 to MAB8 are allocated similarly tothe sixth embodiment.

Referring to FIG. 42, the operation in a normal mode will be nowdescribed. In the normal mode, regardless of an applied address signal(row address signal), power supply switch circuit SW1 provided formemory block MAB1 including spare block SPB is driven into a selectedstate. Before spare determination, the power supply switch circuitcorresponding to a memory block including an addressed word line WL isdriven into a selected state. In FIG. 42, memory block MAB2 includes anaddressed word line WL. In the other memory blocks, the power supplyswitch circuits are maintained in a non-selected state. A sparedetermination as to whether a defective memory cell is addressed isperformed by comparing addresses, and according to the result ofdetermination, an addressed word line or spare word line is driven intoa selected state.

Before the spare determination, a power supply switch circuit for amemory block including a memory cell to be selected (memory blockincluding an addressed word line or spare word line) is driven into aselected state. Therefore, when a word line is driven into a selectedstate in the memory block including the memory cell to be selected, aprescribed voltage is stably supplied, and therefore the memory cell tobe selected can be accurately driven into a selected state. Theoperation will be now more detailed with reference to the signalwaveform diagram in FIG. 43.

When an active cycle is started, array activation signal RACT is driveninto an H level, active state. According to the activation of arrayactivation signal RACT, row address signal RA is made definite, and theaddressed memory block is determined. According to the activation ofarray activation signal RACT, regardless of the applied row addresssignal RA, power supply block selecting signal φB1 to memory block MAB1including a spare block is driven into an active state. According toaddress signal RA, one of memory blocks MAB2 to MAB8 is selected, andcorresponding one of power supply block selecting signals φB2 to φB8 isdriven into a selected state. According to address signal RA, a sparedetermination as to whether a defective row is addressed is made. If theresult of spare determination indicates that a defective row isaddressed (spare hit), a spare word line SWL included in spare block SPBis driven into a selected state. Meanwhile, when it is determined that anormal memory cell in a normal state is addressed (spare miss), a normalword line NWL is driven into a selected state.

When word line NWL or SWL is driven into a selected state, acorresponding power supply switch circuit has been selected to supply aprescribed voltage. Therefore, word line NWL or SWL can be accuratelydriven into a selected state.

When a memory block is selected based on the spare determination, aftera spare hit/miss determination is made, the power supply circuit to acorresponding memory block is driven into a selected state (shown inbroken line in FIG. 43). Thereafter, word line NWL or SWL must be driveninto a selected state, and therefore the timing of activating the wordline should be delayed, which increases the accessing time. However, bydriving the power supply switch circuits to memory block MAB1 and thememory block including the addressed normal word line into a selectedstate before determining whether this defective normal word line hasbeen addressed, a prescribed voltage can be supplied from acorresponding power supply switch circuit within the spare determinationtime period, so that a high speed operation is implemented. (The wordline selecting timing does not have to be delayed.)

Referring to FIGS. 44 and 45, the operation in the self-refresh modewill be now described. In the self-refresh mode, as shown in FIG. 44, apower supply switch circuit is selected according to the result of sparedetermination. Let us now assume that normal word line NWL in memoryblock MAB2 is addressed by refresh address signal QA. A sparedetermination as to whether or not normal word line NWL is defective ismade by comparing the addresses. At this time, a decoding operation isalso executed in parallel for selecting a power supply switch circuit,but the power supply block selecting signals are all maintained in anon-selected state. If a spare hit is determined, spare word line SWLmust be driven into a selected state in place of normal word line NWL.In this case, power supply switch circuit SW1 is driven into a selectedstate based on the spare hit determination result. The other powersupply switch circuits SW2 to SW8 are maintained in a non-selectedstate. Based on the spare hit determination result, spare word line SWLis driven into a selected state, and normal word line NWL is maintainedin a non-selected state.

Meanwhile, if the spare determination result indicates a spare miss,power supply switch circuit SW2 is driven into a selected state, andnormal word line NWL is driven into a selected state.

In the refresh mode, a data accessing is not requested, and thereforethere will be no problem even if the power supply switch circuit isdriven into a selected state after the spare determination. By drivingonly a power supply switch circuit corresponding to a memory blockincluding a memory cell to be selected, the power consumption in therefresh mode can be reduced.

FIG. 46A is a diagram showing an example of a power supply block decodecircuit which generates power supply block selecting signal φB1. In FIG.46A, the power supply block decode circuit includes an NAND circuit 71which receives refresh address bits /QA1, QA2, and QA3, and an NANDcircuit 72 which receives a complimentary array activation signal /RACT,a complimentary spare hit signal /HIT and the output signal of NANDcircuit 71 and outputs power supply block selecting signal φB1. Arrayactivation signal /RACT is set to an L level at the start of an activecycle in the normal mode. Spare hit signal /HIT is set to an L levelwhen a defective cell is addressed. NAND circuit 71 outputs an L levelsignal when memory block MAB1 is addressed. The operation of the powersupply block decode circuit shown in FIG. 46 will be now described withreference to the signal waveform diagram in FIG. 46B.

In the normal mode, when an active cycle is started, complimentary arrayactivation signal /RACT is driven into an L level. Therefore, regardlessof the states of spare hit signal /HIT and the output signal of NANDcircuit 71, power supply block selecting signal φB1 is driven into aactive state. More specifically, when an active cycle is started in thenormal mode, power supply block selecting signal φB1 is driven into aselected state.

In the refresh mode, array activation signal /RACT is fixed at an Hlevel. In the refresh cycle, refresh cycle activation signal QACT isdriven into an H level, active state, and refresh address signal QA isdefined accordingly. When a spare determination is made and a spare hitis determined, spare hit signal /HIT attains an L level, and powersupply block selecting signal φB1 is driven into an H level, selectedstate. Then, a spare word line in a spare block is driven into aselected state.

Meanwhile, when spare hit signal /HIT is at an H level and sparereplacement is not necessary, power supply block selecting signal φB1 isdriven into a selected/non-selected state according to the output signalof NAND circuit 71. When memory block MAB1 is addressed, the outputsignal of NAND circuit 71 attains an L level, and power supply blockselecting signal φB1 is driven into a selected state (H level)accordingly. Meanwhile, if any of the other memory blocks MAB2 to MAB8is addressed, the output signal of NAND circuit 71 is at an H level, andpower supply block selecting signal φB1 maintains its L level.

Note that in the configuration of the power supply block decode circuitshown in FIG. 46A, even if the output signal of NAND circuit 71 ispulled to an L level and corresponding memory block MAB1 is addressedwhen spare hit signal /HIT is at an L level particular problem is notcaused. This is because upon spare hit, memory block MB1 is selected. Inorder to drive power supply block selecting signal φB1 into aselected/non-selected state after the state of spare hit signal /HIT isdefined, spare hit signal HIT is further applied to NAND circuit 71.After spare hit/miss determination result is defined, the output signalof NAND circuit 71 is defined to drive power supply block selectingsignal φB1 into a selected state accordingly.

FIG. 47A is a diagram showing a power supply block decode circuit forpower supply block selecting signal φBj (j=2 to 8). In FIG. 47A, thepower supply block decode circuit includes an inverter circuit 73 whichinverts self-refresh mode instruction signal /SR, an NAND circuit 74which receives a prescribed combination of refresh address bits QA1 toQA3 and /QA1 to/QA3, an NAND circuit 75 which receives self-refresh modeinstruction signal /SR and a prescribed combination of row address bitsRA1 to RA3 and /RA1 to /RA3, an NAND circuit 76 which receives theoutput signal of inverter 73, the output signal of NAND circuit 74 andspare hit signal /HIT, and an NAND circuit 77 which receives the outputsignals of NAND circuits 75 and 76 to generate power supply blockselecting signal φBj(j=2 to 8). Refresh cycle activation signal /QACTmay be used in place of self-refresh mode instruction signal /SR. Theoperation of power supply block decode circuit shown in FIG. 47A will benow described with reference to the signal waveform diagram shown inFIG. 47B.

In the normal mode, when array activation signal RACT is activated, rowaddress signal RA is defined. After row address signal RA is defined,the output signal of NAND circuit 75 attains an H or L level in responseto row address bits RA1 to RA3 and /RA1 to /RA3, because self-refreshmode instruction signal /SR is at an H level in the normal mode. Theoutput signal of NAND circuit 76 is at an H level in the normal mode,and therefore power supply block selecting signal φBj is driven into aselected/non-selected state based on the output signal of NAND circuit75.

Meanwhile, in the self-refresh mode, self-refresh mode instructionsignal /SR attains an L level, and the output signal of NAND circuit 75is set to an H level. Self-refresh mode instruction signal is at an Hlevel. In the self-refresh mode, when refresh cycle activation signalQACT is driven into an H level of active state, refresh address signalQA is defined. A spare determination is made according to this refreshaddress signal QA, and spare hit signal /HIT is driven into an H or Llevel. At the time of a spare hit, spare hit signal /HIT attains an Llevel, the output signal of NAND circuit 76 attains an H level, andpower supply block selecting signal φBj maintains its L level.Meanwhile, if the result of spare determination indicates a spare miss,spare hit signal /HIT maintains its H level. Therefore, power supplyblock selecting signal φBj is driven into a selected/non-selected stateaccording to the output signal of NAND circuit 74.

In the configuration shown in FIG. 47A, in order to prevent power supplyblock selecting signal φBj from being driven into a selected stateaccording to the output signal of NAND circuit 74 before the sparedetermination result is decided, spare hit signal HIT may be provided asan input to NAND circuit 74.

Modification 1

FIG. 48 is a diagram showing a modification of hierarchical power supplyarrangement 1. In the arrangement shown in FIG. 48, word line drivingtiming control circuit 78 changes the activation timing of word linedriving signal φWL according to self-refresh mode instruction signal SR.Word line driving timing control circuit 78 generates word line drivingsignal φWL in the normal mode according to word line activation signalφRX. Meanwhile, in the self refresh mode, this word line driving signalφWL is generated by delaying word line activation signal φRX. Theconfiguration of word line driving timing control circuit 78 is the sameas the configuration shown in FIG. 29. Even if the activation timing ofpower supply block selecting signal φBi is delayed, the word lineselecting timing can be delayed accordingly using word line drivingtiming control circuit 78 and therefore a word line can be accuratelyselected. Word line driving signal φWL determines the activation timingsof both a spare word line and a normal word line.

Modification 2

FIG. 49 is a diagram showing a second modification of hierarchical powersupply arrangement 1 according to the seventh embodiment. FIG. 49 showsthe configuration of a power supply block selecting signal generatingportion. In FIG. 49, the power supply block selecting signal generatingportion includes a multiplexer 80 which responds to self-refresh modeinstruction signal SR to select one of a self-refresh address fromrefresh address counter 25 and internal row address signal RA frommultiplexer 26, an OR circuit 81 which receives array activation signalRACT and count up instruction signal CTJP, a spare determining circuit82 which responds to an activation of the output signal of OR circuit 81to make a spare determination for an address signal applied frommultiplexer 80, a power supply block decode circuit 83 which decodes apower supply block address signal according to an address signal andself-refresh mode instruction signal SR from multiplexer 80 and a sparehit signal HIT from spare hit determining circuit 82, a latch 84 whichlatches a power supply block selecting signal output from power supplydecode circuit 83 according to count up instruction signal CUP, a latch85 which responds to refresh cycle activation signal QACT to take alatch signal from latch 84, and a multiplexer (MUX) 86 which selects oneof the output signals of latch 85 and power supply block decode circuit83.

The power supply block decode circuit 83 is the same in configuration asthose in FIGS. 46A and 47A, and generates power supply block selectingsignal φBi according to self-refresh mode instruction signal SR, sparehit signal HIT and row address signal RA or QA. Latch 84 or 85 has thesame configuration as that in FIG. 38, latch 84 takes and latches theoutput signal of power supply block decode circuit 83 when count upinstruction signal CUP is active, and latch 85 takes and latches theoutput signal of latch 84 when refresh cycle activation signal QACT isinactive and then outputs the latched signal.

Multiplexer 86 selects the output signal of latch 85 for output in theself-refresh mode, and selects the output signal of power supply decodecircuit 83 in the normal mode. Power supply block selecting signal φBifrom multiplexer 86 is applied to the power supply switch circuit.

The power supply block selecting signal generating circuit furtherincludes a latch 87 which latches spare hit signal HIT output by sparehit determining circuit 82 according to count up instruction signal CUP,a latch 88 which takes and transfers the output signal of latch 87according to refresh cycle activation signal QACT, and a multiplexer(MUX) 89 which selects one of spare hit signal HIT output from sparedetermining circuit 82 and a signal output from latch 88. Latches 87 and88 have the same configuration as latches 84 and 85.

Multiplexer 26 selects refresh address signal QA from register 65 in theself-refresh mode, and selects externally applied row address signal RAin the normal mode. Refresh address counter 25 and register 65 have thesame configuration as that in FIG. 36.

In the configuration shown in FIG. 49, spare determining operation andpower supply block decoding operation to be performed in a next cycleare performed in a refresh cycle preceding by one cycle. The results ofdetermining and decoding are output in the next refresh cycle.Therefore, the decoding operation has been completed in the previouscycle, power supply block selecting signal φBi and spare hit signal HITcan be driven into a selected/non-selected state at a high speed in thenext refresh cycle. Thus, the configuration of the word line drivingcontrol portion can be simplified because of no need to delay the wordline selecting timing in the refresh cycle.

In the normal mode, multiplexer 80 selects internal address signal Adfrom multiplexer 26 for application to power supply block decode circuit83 in spare determining circuit 82. Spare hit signal HIT output fromspare determining circuit 82 is selected by multiplexer 89 for output,and a power supply block selecting signal output from power supply blockdecode circuit 83 is selected by multiplexer 86 for output. Latches 84,85, 87 and 88 are bypassed in this normal mode. If an array activationsignal is activated, spare determining circuit 82 performs a determiningoperation and spare hit signal HIT is generated according to the resultof determination. In the normal mode, power supply block decode circuit83 decodes an address signal from multiplexer 80 regardless of thisspare hit signal HIT, and drives a power supply block selecting signalto memory block MAB1 including a spare block and a addressed memoryblock into a selected state.

By using the configuration shown in FIG. 49, the power consumption inthe self-refresh mode can be reduced without increasing the accessingtime in the normal mode.

As described above, by the hierarchical power supply arrangementaccording to the seventh embodiment of the present invention, in thenormal mode, a memory block including a spare block and an addressedmemory block are driven into a selected state regardless of the sparedetermination result, while in the refresh mode, the power supply switchcircuit to an addressed memory block is driven into a selected state, sothat in the normal mode, a voltage from the power supply switch circuitcan be stably supplied before the spare determination result is definedto enable high-speed accessing, while in the refresh mode, a prescribedvoltage is supplied only to minimum necessary memory blocks, resultingin reduced power consumption.

Hierarchical Power Supply Arrangement 2

FIGS. 50A and 50B illustrate the operation of a hierarchical powersupply arrangement 2 according to the seventh embodiment of the presentinvention. In FIG. 50A, in the normal mode, power supply switch circuitsfor both memory block MAB1 including spare block SPB and an addressedmemory block are driven into a selected state in response to anactivation of an array activation signal. In FIG. 50A, memory block MAB2is addressed. When array activation signal RACT is activated and anactive cycle is started, memory block MAB1 including a spare block andaddressed memory block MAB2 are driven into a selected state, so that aprescribed voltage can be supplied at a high speed with no wait for theresult of spare determination.

As shown in FIG. 50B, when a spare determination result is defined,according to the defined result, only the power supply switch circuitfor the memory block including a memory cell to be selected is driveninto a selected state. In FIG. 50B, normal word line NWL in memory blockMAB2 is driven into a selected state, and power supply switch circuitSW2 is held in a selected state, while power supply switch circuit SW1for memory block MAB1 is driven into a non-selected state. After thedetermination result, normal word line NWL is driven into a selectedstate. Therefore, when the selected normal word line is driven, avoltage is supplied stably from power supply switch circuit SW2 and theselected normal word line can be driven into a selected state accuratelyand at a high speed. In addition, since memory block MAB1 is held in anon-selected state, power supply switch circuit SW1 can be driven into anon-selected state, which can reduce the current consumption.

In the refresh mode, as shown in FIG. 44, only the power supply switchcircuit for a memory block including a memory cell to be selected isdriven into a selected state and the other power supply switch circuitsare held in a non-selected state. Thus, the current consumption in therefresh cycle can be reduced.

FIG. 51A is a diagram showing a power supply block decode circuit forpower supply block selecting signal φB1. In FIG. 51A, the power supplyblock decode circuit includes a one-shot pulse generating circuit 90which generates an L level, one-shot pulse signal in response to afalling of array activation signal /RACT, an NAND circuit 91 whichreceives row address bits /RA1, RA2 and RA3, an NAND circuit 92 whichreceives refresh address bits /QA1, QA2 and QA3, and an NAND circuit 93which receives the output signal of one-shot pulse generating circuit90, the output signals of NAND circuits 91 and 92 and spare hit signal/HIT to output power supply block selecting signal φB1. Address bits/RA1, RA2, RA3, /QA1, QA2 and QA3 are at an L level in a stand-by state.The operation of the power supply block decode circuit shown in FIG. 51Awill be described in conjunction with the signal waveform diagram inFIG. 51B.

When an active cycle is started, array activation signal /RACT falls toan L level. In response to the falling of array activation signal /RACT,one-shot pulse generating circuit 90 generates a one-shot pulse which isat an L level for a prescribed period. Power supply block selectingsignal φB1 output from NAND circuit 93 rises to an H level accordingly.Meanwhile, NAND circuit 91 decodes applied address bits /RA1, RA2 andRA3. When memory block MAB1 is addressed, the output signal of NANDcircuit 91 once again attains an L level, power supply block selectingsignal φB1 output from NAND circuit 93 is driven into an H level. Inthis state, regardless of whether a spare word line is used or not,power supply block selecting signal φB1 is at an H level during thisactive cycle period.

Meanwhile, if a memory block different from memory block MAB1 isaddressed, the output signal of NAND circuit 91 attains an H level. Inthis state, spare hit signal HIT is driven into an H or L levelaccording to the result of spare determination before the output signalof one-shot pulse generating circuit 90 rises to an H level. If a normalword line is used, spare hit signal /HIT is maintained at an H level.Therefore, in this state, in response to a rising of the output signalof one-shot pulse generating circuit 90, power supply block selectingsignal φB1 falls to an L level. In this addressed memory block, a row isselected.

If the output signal of NAND circuit 91 is at an H level, and any of theother memory blocks is addressed, power supply block selecting signalφB1 maintains its H level in response to a falling of spare hit signal/HIT to an L level. The pulse width of a pulse signal output fromone-shot pulse generating circuit 90 is set to the time width requiredfor spare hit signal /HIT being defined, so that power supply blockselecting signal φB1 can be driven into a selected/non-selected statebased on the use/nonuse of corresponding memory block MAB1.

FIG. 52 is a diagram showing a power supply block decode circuit forpower supply block selecting signal φBj (J=2 to 8). The power supplyblock decode circuit shown in FIG. 52 is different from the power supplyblock decode circuit shown in FIG. 47A in the following point. Morespecifically, an OR circuit 94 to receive the output signal of NANDcircuit 75 and spare hit signal HIT is provided between NAND circuits 75and 77. The other configuration is the same as that in FIG. 47A andcorresponding portions are denoted by the same reference numerals andthe description is not provided.

In the configuration of the power supply block decode circuit shown inFIG. 52, when an active cycle is started according to address bits RA1to RA3 and /RA1 to /RA3, power supply block selecting signal φBi isdriven into a selected/non-selected state. When spare hit signal HIT isat an L level, power supply block selecting signal φB1 is maintained ina state according to address bits RA1 to RA3 and /RA1 to /RA3 during theactive cycle period. Meanwhile, when spare hit signal HIT is driven intoan H level, the output signal of OR circuit 94 attains an H level. Inthe normal mode, NAND circuit 76 is at an H level. Therefore, inresponse to a rising of spare hit signal HIT, power supply blockselecting signal φBj falls to an L level. Thus, when a spare word lineis used, only the power supply switch circuit for a memory blockincluding a spare block is driven into a selected state, and the powersupply switch circuit for the memory block including this addresseddefective normal word line is driven into a non-selected state.

Note that the operation of the power supply block decode circuit inFIGS. 51A and 52 is the same as the operation of the power supply blockdecode circuit in FIGS. 46A and 47A, and therefore their operationwaveforms are the same as those given in FIGS. 46B and 47B. Morespecifically, in the refresh cycle, only the power supply switch circuitfor a memory block including a memory cell to be driven is driven into aselected state.

Note that the circuit configuration shown in FIG. 49 can be applied tothe configuration of the power supply block decode circuit shown inFIGS. 51 and 52. More specifically, in the refresh mode, based on arefresh address signal from the refresh address counter in the previouscycle, the selected/non-selected state of the power supply blockselecting signal in the next cycle can be determined.

As in the foregoing, according to the seventh embodiment, in the normalmode, an addressed block is driven into a selected state, then only apower supply switch circuit for the memory block including a memory cellrow to be selected is held in a selected state, and therefore thecurrent consumption in the active cycle can be reduced. Furthermore,simultaneously with the start of an active cycle, a power supply switchcircuit corresponding to a memory block including an addressed block anda memory block including a spare block are driven into a selected state,so that the accessing time can be prevented from being increased.

In the foregoing, memory blocks including spare word lines have beendescribed. However, this hierarchical power supply arrangement isapplicable to the configuration for repairing a spare column.

In the above described seventh embodiment, the memory block including aspare block is one in number, but this hierarchical power supplyarrangement according to the seventh embodiment is applicable to thepreviously described first to fifth embodiments. The repeating circuitmay be a sense amplifier to sense and amplify memory cell data.

As in the foregoing, according to the present invention, since sparelines can replace normal lines in a plurality of memory blocks, thespare lines can be efficiently used, and since the flexible redundancyscheme is utilized, the number of spare decoders can be reduced and thearray area can be restrained from increasing.

Furthermore, a power supply switch circuit is provided for each ofmemory blocks, and the number of power supply switch circuits driveninto a selected state is changed between the normal mode and refreshmode, the accessing time is not increased, while the current consumptioncan be reduced. In the arrangement including a spare block, a powersupply switch circuit for the memory block including the spare block isalways driven into a selected state in response to the start of anactive cycle, and therefore a prescribed voltage can be supplied fromthe power supply switch circuit to the spare block with no wait for aspare determination result, so that the accessing time can be restrainedfrom increasing.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A semiconductor memory device capable ofoperating in a normal mode for accessing data and in a refresh mode forholding data, comprising: a power source node for supplying a prescribedvoltage; a plurality of memory blocks each having a plurality of memorycells arranged in a matrix of rows and columns and a repeating circuitgroup including a plurality of repeating circuits each having a commonfunction for performing an operation related to a memory cell selection;a plurality of power source switch circuits provided corresponding tosaid plurality of memory blocks, each of the power source switchcircuits for coupling said power source node and a repeating circuitgroup in a corresponding memory block, said plurality of power sourceswitch circuits each causing a first current flow in a selected stateand a second current flow smaller than said first current in anon-selected state; and control circuitry for selectively driving saidplurality of power source switch circuits into a selected stateaccording. to an address signal such that the number of selected powersource switch circuits is different between said normal mode and saidrefresh mode.
 2. The semiconductor memory device as recited in claim 1,wherein said control circuitry includes a circuit for generating acontrol signal for selecting a power source switch circuit by decoding afirst number of address bits in said normal mode and generating saidcontrol signal by decoding a second number of address bits in saidrefresh mode, said second number being greater than said first number.3. The semiconductor memory device as recited in claim 1, wherein saidplurality of memory blocks are divided into a plurality of global blockseach having a plurality of memory blocks, and said control circuitryincludes a circuit for decoding an address bit specifying a global blockof said plurality of global blocks in said normal mode, and for decodingan address bit specifying a memory block of said plurality of memoryblocks in said refresh mode.
 4. The semiconductor memory device asrecited in claim 1, wherein said plurality of memory blocks each includea plurality of word lines provided corresponding to each row of memorycells, and wherein said semiconductor memory device further comprises,delay circuitry for delaying a timing of driving a word line providedcorresponding to an addressed row into a selected state in said refreshmode behind the timing in said normal mode.
 5. The semiconductor memorydevice as recited in claim 1, wherein said plurality of memory blockseach include a plurality of word lines provided corresponding to memorycell rows, and said control circuitry includes a circuit for generatingsaid control signal in said refresh mode such that a power source switchcircuit provided for a memory block including an addressed word line isselected and power source switch circuits provided corresponding toremaining memory blocks are set in a non-selected state.
 6. Thesemiconductor memory device as recited in claim 1, further comprisingcount circuitry responsive to activation of a count instruction signalfor performing a counting operation to generate a refresh address insaid refresh mode, wherein said control circuitry includes, a firstdecode circuit for decoding a prescribed bit of said refresh address togenerate and latch a next control signal, and a circuit for applying thenext control signal latched by said first decode circuit in response toa refresh cycle instruction signal applied after completion of thedecoding operation by said first decode circuit in said refresh mode,said count instruction signal is activated in an activation period ofsaid refresh cycle instruction signal and said refresh address specifiesa refresh row to be refreshed in a refresh cycle started by said refreshcycle instruction signal.
 7. The semiconductor memory device as recitedin claim 1, wherein a particular memory block of said plurality ofmemory blocks includes a spare element for repairing a defective cell byreplacement, said spare element being capable of repairing a defectivecell in any of said plurality of memory blocks, and said controlcircuitry includes a circuit for selecting a power source switch circuitfor said particular block regardless of said address signal in saidnormal mode and for selectively driving a power source switch circuitprovided corresponding to said particular memory block according to theresult of determination of whether said address signal addresses amemory cell to be repaired in the refresh mode.
 8. The semiconductormemory device as recited in claim 7, further comprising countingcircuitry responsive to a count instruction signal for performing acounting operation to generate a refresh address in said refresh mode,wherein said control circuitry includes, a first decode circuit fordecoding a prescribed bit of said refresh address to generate and latcha next control signal, and a circuit responsive to activation of arefresh cycle instruction signal applied after completion of thedecoding operation by said first decode circuit for applying the controlsignal latched by said first decode circuit to said plurality of powersource switch circuits in said refresh mode, said count instructionsignal is activated in an activation period of said refresh cycleinstruction signal, said refresh address specifying a refresh row in arefresh cycle started by said refresh cycle instruction signal.
 9. Thesemiconductor memory device as recited in claim 7, wherein said controlcircuitry includes a circuit for driving a power source switch circuitprovided corresponding to said particular memory block and a memoryblock specified by said address signal into a selected state, and thendriving into a non-selected state a power source switch circuit providedcorresponding to a memory block excluding a memory block including amemory cell to be driven into a selected state according to the resultof said determination and said address signal in said normal mode. 10.The semiconductor memory devise as recited in claim 1, wherein aparticular memory block of said plurality of memory blocks includes aspare element for repairing a defective cell by replacement, said spareelement being capable of repairing a defective cell in any of saidplurality of memory blocks in said normal mode, and said controlcircuitry includes a circuit for driving a power source switch circuitprovided corresponding to said particular memory block and an addressedmemory block among said plurality of power source switch circuits into aselected state in said normal mode.